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Why am I smoking this step-up regulator?

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  • Don
    I am using this step-up regulator http://www.semtech.com/images/datasheet/sc120.pdf and consistently smoking it. In an attempt to figure out the problem, I
    Message 1 of 30 , Sep 2, 2013
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      I am using this step-up regulator http://www.semtech.com/images/datasheet/sc120.pdf and consistently smoking it. In an attempt to figure out the problem, I have reduced the circuit to the nothing other than the regulator, the 3.7V battery input, three 4.7 uF capacitors (I know they should be 10uF but I substituted the lower values until the right ones arrive - I don't think that is the problem), two resistors to set the output voltage, and an inductor. The inductor seems to be causing the problem - if I remove it there is no smoke - but I don't know why. Could it be that it is the type of inductor I chose? I am using this one http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914. It is the recommended 4.7uH but I see that the datasheet for the regulator suggests some different inductors and I have ordered one of them to test. But if it is the inductor, what was wrong with the one I chose?
    • Jan Kok
      The circuit doesn t smoke without the inductor because no significant current flows without the inductor. So the problem isn t necessarily the inductor. What
      Message 2 of 30 , Sep 2, 2013
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        The circuit doesn't smoke without the inductor because no significant
        current flows without the inductor. So the problem isn't necessarily the
        inductor.

        What sort of capacitors are you using? Did you read the section "Capacitor
        Selection" on page 26 of the datasheet? And do you have an input capacitor?
        That's important too. Without the input capacitor, you have relatively
        large amounts of inductance between the battery and the switcher which
        (aha!?) can cause high voltage spikes on the input pin when the main
        inductor is present. I'd also keep the feedback capacitor, until I was
        absolutely sure it's not needed. But I think it is needed, for "stability",
        i.e. to avoid having the output voltage oscillate and overshoot the desired
        voltage.

        Are you using a PCB with something close to the recommended layout? Wiring
        up a switching power supply on a breadboard is NOT apt to work. The parts
        need to be as close to the power supply chip and the lead lengths need to
        be kept as short as humanly possible.


        On Mon, Sep 2, 2013 at 2:55 PM, Don <DCFrench@...> wrote:

        > I am using this step-up regulator
        > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
        > smoking it. In an attempt to figure out the problem, I have reduced the
        > circuit to the nothing other than the regulator, the 3.7V battery input,
        > three 4.7 uF capacitors (I know they should be 10uF but I substituted the
        > lower values until the right ones arrive - I don't think that is the
        > problem), two resistors to set the output voltage, and an inductor. The
        > inductor seems to be causing the problem - if I remove it there is no smoke
        > - but I don't know why. Could it be that it is the type of inductor I
        > chose? I am using this one
        > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
        > It is the recommended 4.7uH but I see that the datasheet for the regulator
        > suggests some different inductors and I have ordered one of them to test.
        > But if it is the inductor, what was wrong with the one I chose?
        >


        [Non-text portions of this message have been removed]
      • Howard Hansen
        Is one or more output capacitors installed backwards? Is one of the output capacitors faulty? What load resistance are you using? What is the output voltage
        Message 3 of 30 , Sep 2, 2013
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          Is one or more output capacitors installed backwards? Is one of the
          output capacitors faulty? What load resistance are you using? What is
          the output voltage when it is smoking? Is the output voltage compatible
          with you calculated value?

          The other Howard



          On 9/2/2013 3:55 PM, Don wrote
          >
          > I am using this step-up regulator
          > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
          > smoking it. In an attempt to figure out the problem, I have reduced
          > the circuit to the nothing other than the regulator, the 3.7V battery
          > input, three 4.7 uF capacitors (I know they should be 10uF but I
          > substituted the lower values until the right ones arrive - I don't
          > think that is the problem), two resistors to set the output voltage,
          > and an inductor. The inductor seems to be causing the problem - if I
          > remove it there is no smoke - but I don't know why. Could it be that
          > it is the type of inductor I chose? I am using this one
          > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
          > It is the recommended 4.7uH but I see that the datasheet for the
          > regulator suggests some different inductors and I have ordered one of
          > them to test. But if it is the inductor, what was wrong with the one I
          > chose?
          >
          >



          [Non-text portions of this message have been removed]
        • Don
          The circuit has all three of the specified capacitors but they are all 4.7uF, not 10uF. They are ceramic chip capacitors so they don t have polarity. I didn t
          Message 4 of 30 , Sep 2, 2013
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            The circuit has all three of the specified capacitors but they are all 4.7uF, not 10uF. They are ceramic chip capacitors so they don't have polarity. I didn't understand everything in capacitor selection section of the datasheet and am still confused by the table of recommended capacitors - for which cap - they don't say. All my components are SMT on a PCB. My layout is not exactly like that but all the caps and the inductor are quite close to the regulator. The resistors, not so much.

            --- In Electronics_101@yahoogroups.com, Jan Kok <jan.kok.5y@...> wrote:
            >
            > The circuit doesn't smoke without the inductor because no significant
            > current flows without the inductor. So the problem isn't necessarily the
            > inductor.
            >
            > What sort of capacitors are you using? Did you read the section "Capacitor
            > Selection" on page 26 of the datasheet? And do you have an input capacitor?
            > That's important too. Without the input capacitor, you have relatively
            > large amounts of inductance between the battery and the switcher which
            > (aha!?) can cause high voltage spikes on the input pin when the main
            > inductor is present. I'd also keep the feedback capacitor, until I was
            > absolutely sure it's not needed. But I think it is needed, for "stability",
            > i.e. to avoid having the output voltage oscillate and overshoot the desired
            > voltage.
            >
            > Are you using a PCB with something close to the recommended layout? Wiring
            > up a switching power supply on a breadboard is NOT apt to work. The parts
            > need to be as close to the power supply chip and the lead lengths need to
            > be kept as short as humanly possible.
            >
            >
            > On Mon, Sep 2, 2013 at 2:55 PM, Don <DCFrench@...> wrote:
            >
            > > I am using this step-up regulator
            > > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
            > > smoking it. In an attempt to figure out the problem, I have reduced the
            > > circuit to the nothing other than the regulator, the 3.7V battery input,
            > > three 4.7 uF capacitors (I know they should be 10uF but I substituted the
            > > lower values until the right ones arrive - I don't think that is the
            > > problem), two resistors to set the output voltage, and an inductor. The
            > > inductor seems to be causing the problem - if I remove it there is no smoke
            > > - but I don't know why. Could it be that it is the type of inductor I
            > > chose? I am using this one
            > > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
            > > It is the recommended 4.7uH but I see that the datasheet for the regulator
            > > suggests some different inductors and I have ordered one of them to test.
            > > But if it is the inductor, what was wrong with the one I chose?
            > >
            >
            >
            > [Non-text portions of this message have been removed]
            >
          • Jan Kok
            ... ...although it could be. The inductor you are using is only rated for 50mA. The recommended inductors are rated for 500 or 700 mA. Note that the peak
            Message 5 of 30 , Sep 2, 2013
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              On Mon, Sep 2, 2013 at 3:56 PM, Jan Kok <jan.kok.5y@...> wrote:

              > The circuit doesn't smoke without the inductor because no significant
              > current flows without the inductor. So the problem isn't necessarily the
              > inductor.
              >

              ...although it could be. The inductor you are using is only rated for 50mA.
              The recommended inductors are rated for 500 or 700 mA. Note that the peak
              inductor current can be several times the output current. It depends on
              duty cycles and your input and output voltages. If you exceed the rated
              current of the inductor, the inductor saturates and the inductance can
              become much lower than the rated inductance, causing current spikes.


              [Non-text portions of this message have been removed]
            • derekkoonce@att.net
              Derek Koonce ... [Non-text portions of this message have been removed]
              Message 6 of 30 , Sep 2, 2013
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                Derek Koonce

                Jan Kok <jan.kok.5y@...> wrote:


                >
                >On Mon, Sep 2, 2013 at 3:56 PM, Jan Kok <jan.kok.5y@...> wrote:
                >
                >> The circuit doesn't smoke without the inductor because no significant
                >> current flows without the inductor. So the problem isn't necessarily the
                >> inductor.
                >>
                >
                >...although it could be. The inductor you are using is only rated for 50mA.
                >The recommended inductors are rated for 500 or 700 mA. Note that the peak
                >inductor current can be several times the output current. It depends on
                >duty cycles and your input and output voltages. If you exceed the rated
                >current of the inductor, the inductor saturates and the inductance can
                >become much lower than the rated inductance, causing current spikes.
                >
                >[Non-text portions of this message have been removed]
                >
                >
                >
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                [Non-text portions of this message have been removed]
              • derekkoonce@att.net
                Derek Koonce ... [Non-text portions of this message have been removed]
                Message 7 of 30 , Sep 2, 2013
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                  Derek Koonce

                  Jan Kok <jan.kok.5y@...> wrote:


                  >
                  >On Mon, Sep 2, 2013 at 3:56 PM, Jan Kok <jan.kok.5y@...> wrote:
                  >
                  >> The circuit doesn't smoke without the inductor because no significant
                  >> current flows without the inductor. So the problem isn't necessarily the
                  >> inductor.
                  >>
                  >
                  >...although it could be. The inductor you are using is only rated for 50mA.
                  >The recommended inductors are rated for 500 or 700 mA. Note that the peak
                  >inductor current can be several times the output current. It depends on
                  >duty cycles and your input and output voltages. If you exceed the rated
                  >current of the inductor, the inductor saturates and the inductance can
                  >become much lower than the rated inductance, causing current spikes.
                  >
                  >[Non-text portions of this message have been removed]
                  >
                  >
                  >
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                  [Non-text portions of this message have been removed]
                • Jan Kok
                  The output capacitor appears to be most critical: Input and output capacitors must be chosen carefully to ensure that they are of the correct value and
                  Message 8 of 30 , Sep 2, 2013
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                    The output capacitor appears to be most critical: "Input and output
                    capacitors must be chosen carefully to
                    ensure that they are of the correct value and rating. The
                    output capacitor requires a minimum capacitance value
                    of 10�F at the programmed output voltage to ensure stability
                    over the full operating range, and to ensure positive
                    mode-switching hysteresis."

                    They go on to explain: "The DC bias must be included
                    in capacitor derating to ensure the required effective
                    capacitance is provided, especially when considering
                    small package-size capacitors. For example, a 10�F 0805
                    capacitor may provide suffi cient capacitance at low output
                    voltages but may be too low at higher output voltages."

                    They are talking about a non-ideal property of ceramic capacitors: the
                    capacitance at rated voltage is apt to be less than the rated capacitance.
                    Check out a capacitor data sheet and look for a graph of capacitance vs
                    applied voltage. (For example page 121 of
                    http://www.murata.com/products/catalog/pdf/c02e.pdf although there is some
                    critical information missing from that page.)

                    At any rate, it's clear they want at least 10 uF on the output at the power
                    supply output voltage. To get that, you need a capacitor with more than
                    that rated capacitance and/or higher rated capacitor working voltage. The
                    table of recommended capacitors includes a 4.7 uF capacitor. Presumably
                    you'd need at least 3 in parallel to get 10 uF. Since you are only using
                    4.7 uF caps, I'd put several in parallel if you want to get something
                    working ASAP.

                    The input capacitor is not so critical but should be about the same
                    capacitance as the output capacitor. Making it larger might improve
                    efficiency, but probably not much.

                    The feedback capacitor is discussed on page 23 and only needs to be a few
                    pF, if needed at all!


                    On Mon, Sep 2, 2013 at 4:34 PM, Don <DCFrench@...> wrote:

                    > The circuit has all three of the specified capacitors but they are all
                    > 4.7uF, not 10uF. They are ceramic chip capacitors so they don't have
                    > polarity. I didn't understand everything in capacitor selection section of
                    > the datasheet and am still confused by the table of recommended capacitors
                    > - for which cap - they don't say. All my components are SMT on a PCB. My
                    > layout is not exactly like that but all the caps and the inductor are quite
                    > close to the regulator. The resistors, not so much.
                    >
                    > --- In Electronics_101@yahoogroups.com, Jan Kok <jan.kok.5y@...> wrote:
                    > >
                    > > The circuit doesn't smoke without the inductor because no significant
                    > > current flows without the inductor. So the problem isn't necessarily the
                    > > inductor.
                    > >
                    > > What sort of capacitors are you using? Did you read the section
                    > "Capacitor
                    > > Selection" on page 26 of the datasheet? And do you have an input
                    > capacitor?
                    > > That's important too. Without the input capacitor, you have relatively
                    > > large amounts of inductance between the battery and the switcher which
                    > > (aha!?) can cause high voltage spikes on the input pin when the main
                    > > inductor is present. I'd also keep the feedback capacitor, until I was
                    > > absolutely sure it's not needed. But I think it is needed, for
                    > "stability",
                    > > i.e. to avoid having the output voltage oscillate and overshoot the
                    > desired
                    > > voltage.
                    > >
                    > > Are you using a PCB with something close to the recommended layout?
                    > Wiring
                    > > up a switching power supply on a breadboard is NOT apt to work. The parts
                    > > need to be as close to the power supply chip and the lead lengths need to
                    > > be kept as short as humanly possible.
                    > >
                    > >
                    > > On Mon, Sep 2, 2013 at 2:55 PM, Don <DCFrench@...> wrote:
                    > >
                    > > > I am using this step-up regulator
                    > > > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
                    > > > smoking it. In an attempt to figure out the problem, I have reduced
                    > the
                    > > > circuit to the nothing other than the regulator, the 3.7V battery
                    > input,
                    > > > three 4.7 uF capacitors (I know they should be 10uF but I substituted
                    > the
                    > > > lower values until the right ones arrive - I don't think that is the
                    > > > problem), two resistors to set the output voltage, and an inductor.
                    > The
                    > > > inductor seems to be causing the problem - if I remove it there is no
                    > smoke
                    > > > - but I don't know why. Could it be that it is the type of inductor I
                    > > > chose? I am using this one
                    > > >
                    > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914
                    > .
                    > > > It is the recommended 4.7uH but I see that the datasheet for the
                    > regulator
                    > > > suggests some different inductors and I have ordered one of them to
                    > test.
                    > > > But if it is the inductor, what was wrong with the one I chose?
                    >


                    [Non-text portions of this message have been removed]
                  • Don
                    There is no way to install the caps backwards as they don t have polarity. Are you serious about measuring the voltage on a smoking chip? I never would have
                    Message 9 of 30 , Sep 2, 2013
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                      There is no way to install the caps backwards as they don't have polarity.

                      Are you serious about measuring the voltage on a smoking chip? I never would have considered doing that. As soon as it started smoking I pulled the plug. I didn't want it to burst into flames. Smoke is bad enough. There is zero load since, as I said, there is nothing on the board but this circuit.


                      --- In Electronics_101@yahoogroups.com, Howard Hansen <hrhan@...> wrote:
                      >
                      > Is one or more output capacitors installed backwards? Is one of the
                      > output capacitors faulty? What load resistance are you using? What is
                      > the output voltage when it is smoking? Is the output voltage compatible
                      > with you calculated value?
                      >
                      > The other Howard
                      >
                      >
                      >
                      > On 9/2/2013 3:55 PM, Don wrote
                      > >
                      > > I am using this step-up regulator
                      > > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
                      > > smoking it. In an attempt to figure out the problem, I have reduced
                      > > the circuit to the nothing other than the regulator, the 3.7V battery
                      > > input, three 4.7 uF capacitors (I know they should be 10uF but I
                      > > substituted the lower values until the right ones arrive - I don't
                      > > think that is the problem), two resistors to set the output voltage,
                      > > and an inductor. The inductor seems to be causing the problem - if I
                      > > remove it there is no smoke - but I don't know why. Could it be that
                      > > it is the type of inductor I chose? I am using this one
                      > > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
                      > > It is the recommended 4.7uH but I see that the datasheet for the
                      > > regulator suggests some different inductors and I have ordered one of
                      > > them to test. But if it is the inductor, what was wrong with the one I
                      > > chose?
                      > >
                      > >
                      >
                      >
                      >
                      > [Non-text portions of this message have been removed]
                      >
                    • Don
                      I bet you are right about the current rating but maybe 4.7uF caps when it calls for 10uF is the problem too. I just found it hard to imagine - but that was
                      Message 10 of 30 , Sep 2, 2013
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                        I bet you are right about the current rating but maybe 4.7uF caps when it calls for 10uF is the problem too. I just found it hard to imagine - but that was just a gut feeling, not based on science ... Well as soon as the new inductors and the 10uF caps arrive I will try again.

                        --- In Electronics_101@yahoogroups.com, "derekkoonce@..." <derek@...> wrote:
                        >
                        >
                        >
                        > Derek Koonce
                        >
                        > Jan Kok <jan.kok.5y@...> wrote:
                        >
                        > > 
                        > >
                        > >On Mon, Sep 2, 2013 at 3:56 PM, Jan Kok <jan.kok.5y@...> wrote:
                        > >
                        > >> The circuit doesn't smoke without the inductor because no significant
                        > >> current flows without the inductor. So the problem isn't necessarily the
                        > >> inductor.
                        > >>
                        > >
                        > >...although it could be. The inductor you are using is only rated for 50mA.
                        > >The recommended inductors are rated for 500 or 700 mA. Note that the peak
                        > >inductor current can be several times the output current. It depends on
                        > >duty cycles and your input and output voltages. If you exceed the rated
                        > >current of the inductor, the inductor saturates and the inductance can
                        > >become much lower than the rated inductance, causing current spikes.
                        > >
                        > >[Non-text portions of this message have been removed]
                        > >
                        > >
                        > >
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                        >
                        > [Non-text portions of this message have been removed]
                        >
                      • Jan Kok
                        For testing new circuits I d recommend using a bench power supply limited to something reasonable like 20 or 50 mA. A fresh 9V battery can deliver several
                        Message 11 of 30 , Sep 2, 2013
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                          For testing new circuits I'd recommend using a bench power supply limited
                          to something reasonable like 20 or 50 mA. A fresh 9V battery can deliver
                          several amps. Lower voltage batteries of the same physical size can deliver
                          even more current. Real easy to fry things with a battery.

                          If the power supply chip was literally smoking, it's probably toast. I'd
                          just replace it before messing with the circuit any more.


                          On Mon, Sep 2, 2013 at 6:53 PM, Don <DCFrench@...> wrote:

                          > I bet you are right about the current rating but maybe 4.7uF caps when it
                          > calls for 10uF is the problem too. I just found it hard to imagine - but
                          > that was just a gut feeling, not based on science ... Well as soon as the
                          > new inductors and the 10uF caps arrive I will try again.
                          >


                          [Non-text portions of this message have been removed]
                        • Paul Alciatore
                          Some switching regulators need a minimum load to operate properly. Try drawing 10 - 25 mA.
                          Message 12 of 30 , Sep 2, 2013
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                            Some switching regulators need a minimum load to operate properly.
                            Try drawing 10 - 25 mA.
                          • Andy
                            For smaller values and smaller packages, it may be necessary to use multiple devices in parallel, especially for Cout. (From page 26.) You have smaller
                            Message 13 of 30 , Sep 3, 2013
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                              "For smaller values and smaller packages, it may be necessary to use
                              multiple devices in parallel, especially for Cout." (From page 26.)

                              You have smaller values. Did you use multiple devices in parallel for Cout?

                              I haven't looked closely at this part, but it would appear the design
                              may be marginal for stability at only that much (10 uF) capacitance.
                              Anything smaller is ASKING for trouble.

                              Andy
                            • Don
                              This regulator seems a bit complicated for this untrained hacker. Isn t there something simple I can use to get 5V out of a 3.7V LI battery?
                              Message 14 of 30 , Sep 3, 2013
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                                This regulator seems a bit complicated for this untrained hacker. Isn't there something simple I can use to get 5V out of a 3.7V LI battery?

                                --- In Electronics_101@yahoogroups.com, Andy <ai.egrps@...> wrote:
                                >
                                > "For smaller values and smaller packages, it may be necessary to use
                                > multiple devices in parallel, especially for Cout." (From page 26.)
                                >
                                > You have smaller values. Did you use multiple devices in parallel for Cout?
                                >
                                > I haven't looked closely at this part, but it would appear the design
                                > may be marginal for stability at only that much (10 uF) capacitance.
                                > Anything smaller is ASKING for trouble.
                                >
                                > Andy
                                >
                              • Derek
                                Don, Sorry I did not answer earlier - been busy. The circuit is quite basic and, if you are not wanting the output much higher than the 5.0V it should be ok. A
                                Message 15 of 30 , Sep 3, 2013
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                                  Don,

                                  Sorry I did not answer earlier - been busy. The circuit is quite basic
                                  and, if you are not wanting the output much higher than the 5.0V it
                                  should be ok. A couple of things I would note.
                                  1. Check to see if you are exceeding the output voltage. The spec says
                                  6.0V max. If there is no load, then the output can swing above 6V and
                                  burn out the IC.
                                  2. Check the current output. As someone said earlier, the inductor you
                                  selected is good for 50ma. This looks more to be a filtering inductor
                                  and not one to be used for a power supply. The inductor resistance, in
                                  this case, is considered to be high. The inductor you would probably
                                  select would be
                                  http://www.digikey.com/product-detail/en/SRR7032-4R7M/SRR7032-4R7MCT-ND/2127621
                                  (Bourns SRR7032-4R7M)

                                  My DigiKey search, if the link works:
                                  http://www.digikey.com/product-search/en?FV=fff40003%2Cfff80013%2C1c0002%2C1c0003%2C1c0006%2C4c0006%2C1080005%2C108002d%2C1080037%2C108007d%2C1080099%2C108009a%2C108011c%2C108018b%2C10803ea%2C10805ce%2C10809a0%2C1080a10%2C1080aff%2C130c0002%2C130c0015%2C130c0016%2C130c00cd%2C130c0115%2C130c012c%2C130c0150%2C130c0154%2C130c015e%2C130c01d1%2C130c02dc%2C130c030d%2C130c03b5%2C130c03c9%2C130c03e1%2C130c03ed&k=inductor&mnonly=0&newproducts=0&ColumnSort=314&page=1&stock=1&pbfree=0&rohs=0&quantity=&ptm=0&fid=0&pageSize=25

                                  Another quick source would be look up a CoilCraft product and ask for a
                                  couple samples.

                                  Otherwise, I would have to get more information on your design: current
                                  schematic, input and output requirements, etc. This way I have a better
                                  starting point to help you debug.

                                  Derek Koonce
                                  DDK Interactive Consulting Services


                                  On 9/3/2013 8:58 AM, Don wrote:
                                  >
                                  > This regulator seems a bit complicated for this untrained hacker.
                                  > Isn't there something simple I can use to get 5V out of a 3.7V LI battery?
                                  >
                                  > --- In Electronics_101@yahoogroups.com
                                  > <mailto:Electronics_101%40yahoogroups.com>, Andy <ai.egrps@...> wrote:
                                  > >
                                  > > "For smaller values and smaller packages, it may be necessary to use
                                  > > multiple devices in parallel, especially for Cout." (From page 26.)
                                  > >
                                  > > You have smaller values. Did you use multiple devices in parallel
                                  > for Cout?
                                  > >
                                  > > I haven't looked closely at this part, but it would appear the design
                                  > > may be marginal for stability at only that much (10 uF) capacitance.
                                  > > Anything smaller is ASKING for trouble.
                                  > >
                                  > > Andy
                                  > >
                                  >
                                  >



                                  [Non-text portions of this message have been removed]
                                • Howard Hansen
                                  My best guess is not enough inductance. In the description for the boost regulator IC it says the LX pin is shorted to ground during the ON state. Hence
                                  Message 16 of 30 , Sep 3, 2013
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                                    My best guess is not enough inductance. In the description for the
                                    boost regulator IC it says the LX pin is shorted to ground during the
                                    "ON" state. Hence the only thing limiting the current through the
                                    inductor during the "ON" state is the size of the inductance. This is
                                    consistent with your observation that there was no smoke when the
                                    inductor was removed.

                                    Yes I was serious about using a voltmeter to measure the output
                                    voltage. Mostly because a bad device doesn't start smoking
                                    instantaneously. You should have a couple of seconds to make a
                                    measurement. Make sure you connect the voltmeter before you turn the
                                    power on Then turn the power on, make the measurement and immediately
                                    turn the power of if you see smoke or smell an odor.

                                    Better yet if you have a digital storage oscilloscope use it to capture
                                    the start up waveforms before you see smoke or smell an odor.

                                    The other Howard


                                    On 9/2/2013 7:47 PM, Don wrote:
                                    >
                                    > There is no way to install the caps backwards as they don't have
                                    > polarity.
                                    >
                                    > Are you serious about measuring the voltage on a smoking chip? I never
                                    > would have considered doing that. As soon as it started smoking I
                                    > pulled the plug. I didn't want it to burst into flames. Smoke is bad
                                    > enough. There is zero load since, as I said, there is nothing on the
                                    > board but this circuit.
                                    >
                                    > --- In Electronics_101@yahoogroups.com
                                    > <mailto:Electronics_101%40yahoogroups.com>, Howard Hansen <hrhan@...>
                                    > wrote:
                                    > >
                                    > > Is one or more output capacitors installed backwards? Is one of the
                                    > > output capacitors faulty? What load resistance are you using? What is
                                    > > the output voltage when it is smoking? Is the output voltage compatible
                                    > > with you calculated value?
                                    > >
                                    > > The other Howard
                                    > >
                                    > >
                                    > >
                                    > > On 9/2/2013 3:55 PM, Don wrote
                                    > > >
                                    > > > I am using this step-up regulator
                                    > > > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
                                    > > > smoking it. In an attempt to figure out the problem, I have reduced
                                    > > > the circuit to the nothing other than the regulator, the 3.7V battery
                                    > > > input, three 4.7 uF capacitors (I know they should be 10uF but I
                                    > > > substituted the lower values until the right ones arrive - I don't
                                    > > > think that is the problem), two resistors to set the output voltage,
                                    > > > and an inductor. The inductor seems to be causing the problem - if I
                                    > > > remove it there is no smoke - but I don't know why. Could it be that
                                    > > > it is the type of inductor I chose? I am using this one
                                    > > >
                                    > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
                                    >
                                    > > > It is the recommended 4.7uH but I see that the datasheet for the
                                    > > > regulator suggests some different inductors and I have ordered one of
                                    > > > them to test. But if it is the inductor, what was wrong with the
                                    > one I
                                    > > > chose?
                                    > > >
                                    > > >
                                    > >
                                    > >
                                    > >
                                    > > [Non-text portions of this message have been removed]
                                    > >
                                    >
                                    >



                                    [Non-text portions of this message have been removed]
                                  • AlienRelics
                                    Ceramic 4.7uF capacitors are highly voltage sensitive. The capacitance drops drastically at even a few volts. I think the issue is as Jan and Derek suggested,
                                    Message 17 of 30 , Sep 3, 2013
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                                      Ceramic 4.7uF capacitors are highly voltage sensitive. The capacitance drops drastically at even a few volts.

                                      I think the issue is as Jan and Derek suggested, your inductor is rated at far too low a current. When an inductor saturates, it becomes essentially an air core inductor with a -lot- less inductance.

                                      If the chip itself has put off smoke, it is damaged. Anything else you do with it is going to be suspect.

                                      Steve Greenfield AE7HD

                                      --- In Electronics_101@yahoogroups.com, "Don" <DCFrench@...> wrote:
                                      >
                                      > There is no way to install the caps backwards as they don't have polarity.
                                      >
                                      > Are you serious about measuring the voltage on a smoking chip? I never would have considered doing that. As soon as it started smoking I pulled the plug. I didn't want it to burst into flames. Smoke is bad enough. There is zero load since, as I said, there is nothing on the board but this circuit.
                                      >
                                      >
                                    • AlienRelics
                                      Six external parts isn t very complex. You may want instead to use two LiIon batteries in series, and use a low-dropout linear regulator. However, you ll still
                                      Message 18 of 30 , Sep 3, 2013
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                                        Six external parts isn't very complex.

                                        You may want instead to use two LiIon batteries in series, and use a low-dropout linear regulator.

                                        However, you'll still need pretty much everything there except an inductor. Input and output capacitors, voltage set resistors, possibly a feedback capacitor.

                                        Steve Greenfield AE7HD


                                        --- In Electronics_101@yahoogroups.com, "Don" <DCFrench@...> wrote:
                                        >
                                        > This regulator seems a bit complicated for this untrained hacker. Isn't there something simple I can use to get 5V out of a 3.7V LI battery?
                                        >
                                        > --- In Electronics_101@yahoogroups.com, Andy <ai.egrps@> wrote:
                                        > >
                                        > > "For smaller values and smaller packages, it may be necessary to use
                                        > > multiple devices in parallel, especially for Cout." (From page 26.)
                                        > >
                                        > > You have smaller values. Did you use multiple devices in parallel for Cout?
                                        > >
                                        > > I haven't looked closely at this part, but it would appear the design
                                        > > may be marginal for stability at only that much (10 uF) capacitance.
                                        > > Anything smaller is ASKING for trouble.
                                        > >
                                        > > Andy
                                        > >
                                        >
                                      • Howard Hansen
                                        If you have an oscilloscope there is a test you could perform to help you decide whether the SC120 or the inductor is faulty. The test involves temporarily
                                        Message 19 of 30 , Sep 4, 2013
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                                          If you have an oscilloscope there is a test you could perform to help you decide whether the SC120 or the inductor is faulty.  The test involves temporarily replacing the inductor with a 1k ohm resistor, temporarily replacing the two feedback resistors with a 100k ohm potentiometer and monitoring the Lx pin with an oscilloscope.   Connect one end of the potentiometer to Vin, the other end to ground and the wiper to the FB pin. Initially set the potentiometer wiper to approximately the mid position and connect the SC120 to its power source.

                                          You should see the signal at the LX pin switching between Vin and ground at the SC120 switching frequency.  Because the SC120 has a built in oscillator its switching frequency is not affected by the value of external components.  Hence if the Lx pin is stuck on ground it implies the SC120 is faulty.  If the LX pin switches between Vin and ground it implies the inductor is faulty. 

                                          If the Lx pin is switching between Vin and ground vary the potentiometers wiper position.   The duty cycle of the switching frequency should vary. 

                                          The other Howard




                                          On 9/3/2013 2:08 PM, Howard Hansen wrote:
                                           

                                          My best guess is not enough inductance. In the description for the
                                          boost regulator IC it says the LX pin is shorted to ground during the
                                          "ON" state. Hence the only thing limiting the current through the
                                          inductor during the "ON" state is the size of the inductance. This is
                                          consistent with your observation that there was no smoke when the
                                          inductor was removed.

                                          Yes I was serious about using a voltmeter to measure the output
                                          voltage. Mostly because a bad device doesn't start smoking
                                          instantaneously. You should have a couple of seconds to make a
                                          measurement. Make sure you connect the voltmeter before you turn the
                                          power on Then turn the power on, make the measurement and immediately
                                          turn the power of if you see smoke or smell an odor.

                                          Better yet if you have a digital storage oscilloscope use it to capture
                                          the start up waveforms before you see smoke or smell an odor.

                                          The other Howard

                                          On 9/2/2013 7:47 PM, Don wrote:
                                          >
                                          > There is no way to install the caps backwards as they don't have
                                          > polarity.
                                          >
                                          > Are you serious about measuring the voltage on a smoking chip? I never
                                          > would have considered doing that. As soon as it started smoking I
                                          > pulled the plug. I didn't want it to burst into flames. Smoke is bad
                                          > enough. There is zero load since, as I said, there is nothing on the
                                          > board but this circuit.
                                          >
                                          > --- In Electronics_101@yahoogroups.com
                                          > <mailto:Electronics_101%40yahoogroups.com>, Howard Hansen <hrhan@...>
                                          > wrote:
                                          > >
                                          > > Is one or more output capacitors installed backwards? Is one of the
                                          > > output capacitors faulty? What load resistance are you using? What is
                                          > > the output voltage when it is smoking? Is the output voltage compatible
                                          > > with you calculated value?
                                          > >
                                          > > The other Howard
                                          > >
                                          > >
                                          > >
                                          > > On 9/2/2013 3:55 PM, Don wrote
                                          > > >
                                          > > > I am using this step-up regulator
                                          > > > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
                                          > > > smoking it. In an attempt to figure out the problem, I have reduced
                                          > > > the circuit to the nothing other than the regulator, the 3.7V battery
                                          > > > input, three 4.7 uF capacitors (I know they should be 10uF but I
                                          > > > substituted the lower values until the right ones arrive - I don't
                                          > > > think that is the problem), two resistors to set the output voltage,
                                          > > > and an inductor. The inductor seems to be causing the problem - if I
                                          > > > remove it there is no smoke - but I don't know why. Could it be that
                                          > > > it is the type of inductor I chose? I am using this one
                                          > > >
                                          > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
                                          >
                                          > > > It is the recommended 4.7uH but I see that the datasheet for the
                                          > > > regulator suggests some different inductors and I have ordered one of
                                          > > > them to test. But if it is the inductor, what was wrong with the
                                          > one I
                                          > > > chose?
                                          > > >
                                          > > >
                                          > >
                                          > >
                                          > >
                                          > > [Non-text portions of this message have been removed]
                                          > >
                                          >
                                          >

                                          [Non-text portions of this message have been removed]


                                        • Don
                                          Thanks but you know none of that is very easy to do when everything is surface mounted. It is far easier to just try replacing the inductor and the caps with
                                          Message 20 of 30 , Sep 4, 2013
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                                            Thanks but you know none of that is very easy to do when everything is surface mounted. It is far easier to just try replacing the inductor and the caps with values that seem to be more reasonable and seeing if that fixes it. BTW, It definitely isn't the regulator - I have smoked three of them already.

                                            Anyway, I am seriously considering switching to a different regulator for which there exists a well-tested circuit and even Eagle files and a list of the exact components.

                                            I refer to this circuit http://www.sparkfun.com/datasheets/Prototyping/LiPower-v11.pdf/ But with this regulator a new problem arises and maybe someone can advise me on it. The regulator has a large pad on its bottom. How do I solder that thing? Toaster oven?

                                            --- In Electronics_101@yahoogroups.com, Howard Hansen <hrhan@...> wrote:
                                            >
                                            > If you have an oscilloscope there is a test you could perform to help
                                            > you decide whether the SC120 or the inductor is faulty. The test
                                            > involves temporarily replacing the inductor with a 1k ohm resistor,
                                            > temporarily replacing the two feedback resistors with a 100k ohm
                                            > potentiometer and monitoring the Lx pin with an oscilloscope. Connect
                                            > one end of the potentiometer to Vin, the other end to ground and the
                                            > wiper to the FB pin. Initially set the potentiometer wiper to
                                            > approximately the mid position and connect the SC120 to its power source.
                                            >
                                            > You should see the signal at the LX pin switching between Vin and ground
                                            > at the SC120 switching frequency. Because the SC120 has a built in
                                            > oscillator its switching frequency is not affected by the value of
                                            > external components. Hence if the Lx pin is stuck on ground it implies
                                            > the SC120 is faulty. If the LX pin switches between Vin and ground it
                                            > implies the inductor is faulty.
                                            >
                                            > If the Lx pin is switching between Vin and ground vary the
                                            > potentiometers wiper position. The duty cycle of the switching
                                            > frequency should vary.
                                            >
                                            > The other Howard
                                            >
                                            >
                                            >
                                            >
                                            > On 9/3/2013 2:08 PM, Howard Hansen wrote:
                                            > >
                                            > > My best guess is not enough inductance. In the description for the
                                            > > boost regulator IC it says the LX pin is shorted to ground during the
                                            > > "ON" state. Hence the only thing limiting the current through the
                                            > > inductor during the "ON" state is the size of the inductance. This is
                                            > > consistent with your observation that there was no smoke when the
                                            > > inductor was removed.
                                            > >
                                            > > Yes I was serious about using a voltmeter to measure the output
                                            > > voltage. Mostly because a bad device doesn't start smoking
                                            > > instantaneously. You should have a couple of seconds to make a
                                            > > measurement. Make sure you connect the voltmeter before you turn the
                                            > > power on Then turn the power on, make the measurement and immediately
                                            > > turn the power of if you see smoke or smell an odor.
                                            > >
                                            > > Better yet if you have a digital storage oscilloscope use it to capture
                                            > > the start up waveforms before you see smoke or smell an odor.
                                            > >
                                            > > The other Howard
                                            > >
                                            > > On 9/2/2013 7:47 PM, Don wrote:
                                            > > >
                                            > > > There is no way to install the caps backwards as they don't have
                                            > > > polarity.
                                            > > >
                                            > > > Are you serious about measuring the voltage on a smoking chip? I never
                                            > > > would have considered doing that. As soon as it started smoking I
                                            > > > pulled the plug. I didn't want it to burst into flames. Smoke is bad
                                            > > > enough. There is zero load since, as I said, there is nothing on the
                                            > > > board but this circuit.
                                            > > >
                                            > > > --- In Electronics_101@yahoogroups.com
                                            > > <mailto:Electronics_101%40yahoogroups.com>
                                            > > > <mailto:Electronics_101%40yahoogroups.com>, Howard Hansen <hrhan@>
                                            > > > wrote:
                                            > > > >
                                            > > > > Is one or more output capacitors installed backwards? Is one of the
                                            > > > > output capacitors faulty? What load resistance are you using? What is
                                            > > > > the output voltage when it is smoking? Is the output voltage
                                            > > compatible
                                            > > > > with you calculated value?
                                            > > > >
                                            > > > > The other Howard
                                            > > > >
                                            > > > >
                                            > > > >
                                            > > > > On 9/2/2013 3:55 PM, Don wrote
                                            > > > > >
                                            > > > > > I am using this step-up regulator
                                            > > > > > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
                                            > > > > > smoking it. In an attempt to figure out the problem, I have reduced
                                            > > > > > the circuit to the nothing other than the regulator, the 3.7V
                                            > > battery
                                            > > > > > input, three 4.7 uF capacitors (I know they should be 10uF but I
                                            > > > > > substituted the lower values until the right ones arrive - I don't
                                            > > > > > think that is the problem), two resistors to set the output voltage,
                                            > > > > > and an inductor. The inductor seems to be causing the problem - if I
                                            > > > > > remove it there is no smoke - but I don't know why. Could it be that
                                            > > > > > it is the type of inductor I chose? I am using this one
                                            > > > > >
                                            > > >
                                            > > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
                                            > >
                                            > > >
                                            > > > > > It is the recommended 4.7uH but I see that the datasheet for the
                                            > > > > > regulator suggests some different inductors and I have ordered
                                            > > one of
                                            > > > > > them to test. But if it is the inductor, what was wrong with the
                                            > > > one I
                                            > > > > > chose?
                                            > > > > >
                                            > > > > >
                                            > > > >
                                            > > > >
                                            > > > >
                                            > > > > [Non-text portions of this message have been removed]
                                            > > > >
                                            > > >
                                            > > >
                                            > >
                                            > > [Non-text portions of this message have been removed]
                                            > >
                                            > >
                                            >
                                          • Stefan Trethan
                                            Oven, hotplate, or hot air. That crazy aussie bloke has a video on youtube showing how you can do it with just an iron if there are vias:
                                            Message 21 of 30 , Sep 4, 2013
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                                              Oven, hotplate, or hot air.

                                              That crazy aussie bloke has a video on youtube showing how you can do it with just an iron if there are vias:
                                              ST

                                              On Thu, Sep 5, 2013 at 6:07 AM, Don <DCFrench@...> wrote:
                                              The regulator has a large pad on its bottom.  How do I solder that thing?  Toaster oven?



                                            • Don
                                              Thanks! I just learned quite a lot from that crazy Aussie bloke.
                                              Message 22 of 30 , Sep 5, 2013
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                                                Thanks! I just learned quite a lot from that crazy Aussie bloke.


                                                --- In Electronics_101@yahoogroups.com, Stefan Trethan <stefan_trethan@...> wrote:
                                                >
                                                > Oven, hotplate, or hot air.
                                                >
                                                > That crazy aussie bloke has a video on youtube showing how you can do it
                                                > with just an iron if there are vias:
                                                > <http://www.youtube.com/watch?v=588iV07nEdM>
                                                >
                                                > ST
                                                >
                                                > On Thu, Sep 5, 2013 at 6:07 AM, Don <DCFrench@...> wrote:
                                                >
                                                > > The regulator has a large pad on its bottom. How do I solder that thing?
                                                > > Toaster oven?
                                                > >
                                                > >
                                                > >
                                                >
                                              • Don
                                                I was going to try that iron technique but got stymied at first when I could find no way to make a pad on the opposite side of the board. Also, the smallest
                                                Message 23 of 30 , Sep 5, 2013
                                                • 0 Attachment
                                                  I was going to try that iron technique but got stymied at first when I could find no way to make a pad on the opposite side of the board. Also, the smallest via I can make (with Eagle) is rather large - larger than the vias that the autorouter makes and certainly larger than the ones he made. I kind of hate to remove that much of the heat sink surface. I think I solved the first problem by adding another regulator to the schematic but not wiring up any of its pins and then placing it on the opposite side of the board from the first one. Maybe I can solve the second problem by filling the vias after the part is soldered on - or maybe they will fill in automatically. Worth a try, I guess.

                                                  --- In Electronics_101@yahoogroups.com, "Don" <DCFrench@...> wrote:
                                                  >
                                                  > Thanks! I just learned quite a lot from that crazy Aussie bloke.
                                                  >
                                                  >
                                                  > --- In Electronics_101@yahoogroups.com, Stefan Trethan <stefan_trethan@> wrote:
                                                  > >
                                                  > > Oven, hotplate, or hot air.
                                                  > >
                                                  > > That crazy aussie bloke has a video on youtube showing how you can do it
                                                  > > with just an iron if there are vias:
                                                  > > <http://www.youtube.com/watch?v=588iV07nEdM>
                                                  > >
                                                  > > ST
                                                  > >
                                                  > > On Thu, Sep 5, 2013 at 6:07 AM, Don <DCFrench@> wrote:
                                                  > >
                                                  > > > The regulator has a large pad on its bottom. How do I solder that thing?
                                                  > > > Toaster oven?
                                                  > > >
                                                  > > >
                                                  > > >
                                                  > >
                                                  >
                                                • Howard Hansen
                                                  Now that you mention Sparkfun I am curious as to why you are building a boost converter and not using this one. The
                                                  Message 24 of 30 , Sep 5, 2013
                                                  • 0 Attachment
                                                    Now that you mention Sparkfun I am curious as to why you are building a boost converter and not using this one.
                                                    <https://www.sparkfun.com/products/10255>

                                                    The other Howard



                                                    On 9/4/2013 11:07 PM, Don wrote:
                                                     

                                                    Thanks but you know none of that is very easy to do when everything is surface mounted. It is far easier to just try replacing the inductor and the caps with values that seem to be more reasonable and seeing if that fixes it. BTW, It definitely isn't the regulator - I have smoked three of them already.

                                                    Anyway, I am seriously considering switching to a different regulator for which there exists a well-tested circuit and even Eagle files and a list of the exact components.

                                                    I refer to this circuit http://www.sparkfun.com/datasheets/Prototyping/LiPower-v11.pdf/ But with this regulator a new problem arises and maybe someone can advise me on it. The regulator has a large pad on its bottom. How do I solder that thing? Toaster oven?

                                                    --- In Electronics_101@yahoogroups.com, Howard Hansen <hrhan@...> wrote:
                                                    >
                                                    > If you have an oscilloscope there is a test you could perform to help
                                                    > you decide whether the SC120 or the inductor is faulty. The test
                                                    > involves temporarily replacing the inductor with a 1k ohm resistor,
                                                    > temporarily replacing the two feedback resistors with a 100k ohm
                                                    > potentiometer and monitoring the Lx pin with an oscilloscope. Connect
                                                    > one end of the potentiometer to Vin, the other end to ground and the
                                                    > wiper to the FB pin. Initially set the potentiometer wiper to
                                                    > approximately the mid position and connect the SC120 to its power source.
                                                    >
                                                    > You should see the signal at the LX pin switching between Vin and ground
                                                    > at the SC120 switching frequency. Because the SC120 has a built in
                                                    > oscillator its switching frequency is not affected by the value of
                                                    > external components. Hence if the Lx pin is stuck on ground it implies
                                                    > the SC120 is faulty. If the LX pin switches between Vin and ground it
                                                    > implies the inductor is faulty.
                                                    >
                                                    > If the Lx pin is switching between Vin and ground vary the
                                                    > potentiometers wiper position. The duty cycle of the switching
                                                    > frequency should vary.
                                                    >
                                                    > The other Howard
                                                    >
                                                    >
                                                    >
                                                    >
                                                    > On 9/3/2013 2:08 PM, Howard Hansen wrote:
                                                    > >
                                                    > > My best guess is not enough inductance. In the description for the
                                                    > > boost regulator IC it says the LX pin is shorted to ground during the
                                                    > > "ON" state. Hence the only thing limiting the current through the
                                                    > > inductor during the "ON" state is the size of the inductance. This is
                                                    > > consistent with your observation that there was no smoke when the
                                                    > > inductor was removed.
                                                    > >
                                                    > > Yes I was serious about using a voltmeter to measure the output
                                                    > > voltage. Mostly because a bad device doesn't start smoking
                                                    > > instantaneously. You should have a couple of seconds to make a
                                                    > > measurement. Make sure you connect the voltmeter before you turn the
                                                    > > power on Then turn the power on, make the measurement and immediately
                                                    > > turn the power of if you see smoke or smell an odor.
                                                    > >
                                                    > > Better yet if you have a digital storage oscilloscope use it to capture
                                                    > > the start up waveforms before you see smoke or smell an odor.
                                                    > >
                                                    > > The other Howard
                                                    > >
                                                    > > On 9/2/2013 7:47 PM, Don wrote:
                                                    > > >
                                                    > > > There is no way to install the caps backwards as they don't have
                                                    > > > polarity.
                                                    > > >
                                                    > > > Are you serious about measuring the voltage on a smoking chip? I never
                                                    > > > would have considered doing that. As soon as it started smoking I
                                                    > > > pulled the plug. I didn't want it to burst into flames. Smoke is bad
                                                    > > > enough. There is zero load since, as I said, there is nothing on the
                                                    > > > board but this circuit.
                                                    > > >
                                                    > > > --- In Electronics_101@yahoogroups.com
                                                    > > <mailto:Electronics_101%40yahoogroups.com>
                                                    > > > <mailto:Electronics_101%40yahoogroups.com>, Howard Hansen <hrhan@>
                                                    > > > wrote:
                                                    > > > >
                                                    > > > > Is one or more output capacitors installed backwards? Is one of the
                                                    > > > > output capacitors faulty? What load resistance are you using? What is
                                                    > > > > the output voltage when it is smoking? Is the output voltage
                                                    > > compatible
                                                    > > > > with you calculated value?
                                                    > > > >
                                                    > > > > The other Howard
                                                    > > > >
                                                    > > > >
                                                    > > > >
                                                    > > > > On 9/2/2013 3:55 PM, Don wrote
                                                    > > > > >
                                                    > > > > > I am using this step-up regulator
                                                    > > > > > http://www.semtech.com/images/datasheet/sc120.pdf and consistently
                                                    > > > > > smoking it. In an attempt to figure out the problem, I have reduced
                                                    > > > > > the circuit to the nothing other than the regulator, the 3.7V
                                                    > > battery
                                                    > > > > > input, three 4.7 uF capacitors (I know they should be 10uF but I
                                                    > > > > > substituted the lower values until the right ones arrive - I don't
                                                    > > > > > think that is the problem), two resistors to set the output voltage,
                                                    > > > > > and an inductor. The inductor seems to be causing the problem - if I
                                                    > > > > > remove it there is no smoke - but I don't know why. Could it be that
                                                    > > > > > it is the type of inductor I chose? I am using this one
                                                    > > > > >
                                                    > > >
                                                    > > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
                                                    > >
                                                    > > >
                                                    > > > > > It is the recommended 4.7uH but I see that the datasheet for the
                                                    > > > > > regulator suggests some different inductors and I have ordered
                                                    > > one of
                                                    > > > > > them to test. But if it is the inductor, what was wrong with the
                                                    > > > one I
                                                    > > > > > chose?
                                                    > > > > >
                                                    > > > > >
                                                    > > > >
                                                    > > > >
                                                    > > > >
                                                    > > > > [Non-text portions of this message have been removed]
                                                    > > > >
                                                    > > >
                                                    > > >
                                                    > >
                                                    > > [Non-text portions of this message have been removed]
                                                    > >
                                                    > >
                                                    >


                                                  • Don
                                                    Because it is going into a single board product and I plan on making them in volume.
                                                    Message 25 of 30 , Sep 5, 2013
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                                                      Because it is going into a single board product and I plan on making them in volume.

                                                      --- In Electronics_101@yahoogroups.com, Howard Hansen <hrhan@...> wrote:
                                                      >
                                                      > Now that you mention Sparkfun I am curious as to why you are building a
                                                      > boost converter and not using this one.
                                                      > <https://www.sparkfun.com/products/10255>
                                                      >
                                                      > The other Howard
                                                      >
                                                      >
                                                      >
                                                      > On 9/4/2013 11:07 PM, Don wrote:
                                                      > >
                                                      > > Thanks but you know none of that is very easy to do when everything is
                                                      > > surface mounted. It is far easier to just try replacing the inductor
                                                      > > and the caps with values that seem to be more reasonable and seeing if
                                                      > > that fixes it. BTW, It definitely isn't the regulator - I have smoked
                                                      > > three of them already.
                                                      > >
                                                      > > Anyway, I am seriously considering switching to a different regulator
                                                      > > for which there exists a well-tested circuit and even Eagle files and
                                                      > > a list of the exact components.
                                                      > >
                                                      > > I refer to this circuit
                                                      > > http://www.sparkfun.com/datasheets/Prototyping/LiPower-v11.pdf/ But
                                                      > > with this regulator a new problem arises and maybe someone can advise
                                                      > > me on it. The regulator has a large pad on its bottom. How do I solder
                                                      > > that thing? Toaster oven?
                                                      > >
                                                      > > --- In Electronics_101@yahoogroups.com, Howard Hansen <hrhan@> wrote:
                                                      > > >
                                                      > > > If you have an oscilloscope there is a test you could perform to help
                                                      > > > you decide whether the SC120 or the inductor is faulty. The test
                                                      > > > involves temporarily replacing the inductor with a 1k ohm resistor,
                                                      > > > temporarily replacing the two feedback resistors with a 100k ohm
                                                      > > > potentiometer and monitoring the Lx pin with an oscilloscope. Connect
                                                      > > > one end of the potentiometer to Vin, the other end to ground and the
                                                      > > > wiper to the FB pin. Initially set the potentiometer wiper to
                                                      > > > approximately the mid position and connect the SC120 to its power
                                                      > > source.
                                                      > > >
                                                      > > > You should see the signal at the LX pin switching between Vin and
                                                      > > ground
                                                      > > > at the SC120 switching frequency. Because the SC120 has a built in
                                                      > > > oscillator its switching frequency is not affected by the value of
                                                      > > > external components. Hence if the Lx pin is stuck on ground it implies
                                                      > > > the SC120 is faulty. If the LX pin switches between Vin and ground it
                                                      > > > implies the inductor is faulty.
                                                      > > >
                                                      > > > If the Lx pin is switching between Vin and ground vary the
                                                      > > > potentiometers wiper position. The duty cycle of the switching
                                                      > > > frequency should vary.
                                                      > > >
                                                      > > > The other Howard
                                                      > > >
                                                      > > >
                                                      > > >
                                                      > > >
                                                      > > > On 9/3/2013 2:08 PM, Howard Hansen wrote:
                                                      > > > >
                                                      > > > > My best guess is not enough inductance. In the description for the
                                                      > > > > boost regulator IC it says the LX pin is shorted to ground during the
                                                      > > > > "ON" state. Hence the only thing limiting the current through the
                                                      > > > > inductor during the "ON" state is the size of the inductance. This is
                                                      > > > > consistent with your observation that there was no smoke when the
                                                      > > > > inductor was removed.
                                                      > > > >
                                                      > > > > Yes I was serious about using a voltmeter to measure the output
                                                      > > > > voltage. Mostly because a bad device doesn't start smoking
                                                      > > > > instantaneously. You should have a couple of seconds to make a
                                                      > > > > measurement. Make sure you connect the voltmeter before you turn the
                                                      > > > > power on Then turn the power on, make the measurement and immediately
                                                      > > > > turn the power of if you see smoke or smell an odor.
                                                      > > > >
                                                      > > > > Better yet if you have a digital storage oscilloscope use it to
                                                      > > capture
                                                      > > > > the start up waveforms before you see smoke or smell an odor.
                                                      > > > >
                                                      > > > > The other Howard
                                                      > > > >
                                                      > > > > On 9/2/2013 7:47 PM, Don wrote:
                                                      > > > > >
                                                      > > > > > There is no way to install the caps backwards as they don't have
                                                      > > > > > polarity.
                                                      > > > > >
                                                      > > > > > Are you serious about measuring the voltage on a smoking chip? I
                                                      > > never
                                                      > > > > > would have considered doing that. As soon as it started smoking I
                                                      > > > > > pulled the plug. I didn't want it to burst into flames. Smoke is bad
                                                      > > > > > enough. There is zero load since, as I said, there is nothing on the
                                                      > > > > > board but this circuit.
                                                      > > > > >
                                                      > > > > > --- In Electronics_101@yahoogroups.com
                                                      > > > > <mailto:Electronics_101%40yahoogroups.com>
                                                      > > > > > <mailto:Electronics_101%40yahoogroups.com>, Howard Hansen <hrhan@>
                                                      > > > > > wrote:
                                                      > > > > > >
                                                      > > > > > > Is one or more output capacitors installed backwards? Is one
                                                      > > of the
                                                      > > > > > > output capacitors faulty? What load resistance are you using?
                                                      > > What is
                                                      > > > > > > the output voltage when it is smoking? Is the output voltage
                                                      > > > > compatible
                                                      > > > > > > with you calculated value?
                                                      > > > > > >
                                                      > > > > > > The other Howard
                                                      > > > > > >
                                                      > > > > > >
                                                      > > > > > >
                                                      > > > > > > On 9/2/2013 3:55 PM, Don wrote
                                                      > > > > > > >
                                                      > > > > > > > I am using this step-up regulator
                                                      > > > > > > > http://www.semtech.com/images/datasheet/sc120.pdf and
                                                      > > consistently
                                                      > > > > > > > smoking it. In an attempt to figure out the problem, I have
                                                      > > reduced
                                                      > > > > > > > the circuit to the nothing other than the regulator, the 3.7V
                                                      > > > > battery
                                                      > > > > > > > input, three 4.7 uF capacitors (I know they should be 10uF but I
                                                      > > > > > > > substituted the lower values until the right ones arrive - I
                                                      > > don't
                                                      > > > > > > > think that is the problem), two resistors to set the output
                                                      > > voltage,
                                                      > > > > > > > and an inductor. The inductor seems to be causing the
                                                      > > problem - if I
                                                      > > > > > > > remove it there is no smoke - but I don't know why. Could it
                                                      > > be that
                                                      > > > > > > > it is the type of inductor I chose? I am using this one
                                                      > > > > > > >
                                                      > > > > >
                                                      > > > >
                                                      > > http://www.digikey.com/product-detail/en/AIML-1206-4R7K-T/535-11673-1-ND/2782914.
                                                      > >
                                                      > > > >
                                                      > > > > >
                                                      > > > > > > > It is the recommended 4.7uH but I see that the datasheet for the
                                                      > > > > > > > regulator suggests some different inductors and I have ordered
                                                      > > > > one of
                                                      > > > > > > > them to test. But if it is the inductor, what was wrong with the
                                                      > > > > > one I
                                                      > > > > > > > chose?
                                                      > > > > > > >
                                                      > > > > > > >
                                                      > > > > > >
                                                      > > > > > >
                                                      > > > > > >
                                                      > > > > > > [Non-text portions of this message have been removed]
                                                      > > > > > >
                                                      > > > > >
                                                      > > > > >
                                                      > > > >
                                                      > > > > [Non-text portions of this message have been removed]
                                                      > > > >
                                                      > > > >
                                                      > > >
                                                      > >
                                                      > >
                                                      >
                                                    • Nathan McCorkle
                                                      Did you ever actually try the circuit with the datasheet-recommended configuration? It specifically mentions needing /at least/ 10uF, and mentions not to use
                                                      Message 26 of 30 , Sep 5, 2013
                                                      • 0 Attachment
                                                        Did you ever actually try the circuit with the datasheet-recommended configuration? It specifically mentions needing /at least/ 10uF, and mentions not to use tantalum, recommending ceramic X5R X7R caps instead.


                                                        On Thu, Sep 5, 2013 at 10:15 AM, Don <DCFrench@...> wrote:
                                                         

                                                        I was going to try that iron technique but got stymied at first when I could find no way to make a pad on the opposite side of the board. Also, the smallest via I can make (with Eagle) is rather large - larger than the vias that the autorouter makes and certainly larger than the ones he made. I kind of hate to remove that much of the heat sink surface. I think I solved the first problem by adding another regulator to the schematic but not wiring up any of its pins and then placing it on the opposite side of the board from the first one. Maybe I can solve the second problem by filling the vias after the part is soldered on - or maybe they will fill in automatically. Worth a try, I guess.



                                                        --- In Electronics_101@yahoogroups.com, "Don" <DCFrench@...> wrote:
                                                        >
                                                        > Thanks! I just learned quite a lot from that crazy Aussie bloke.
                                                        >
                                                        >
                                                        > --- In Electronics_101@yahoogroups.com, Stefan Trethan <stefan_trethan@> wrote:
                                                        > >
                                                        > > Oven, hotplate, or hot air.
                                                        > >
                                                        > > That crazy aussie bloke has a video on youtube showing how you can do it
                                                        > > with just an iron if there are vias:
                                                        > > <http://www.youtube.com/watch?v=588iV07nEdM>
                                                        > >
                                                        > > ST
                                                        > >
                                                        > > On Thu, Sep 5, 2013 at 6:07 AM, Don <DCFrench@> wrote:
                                                        > >
                                                        > > > The regulator has a large pad on its bottom. How do I solder that thing?
                                                        > > > Toaster oven?
                                                        > > >
                                                        > > >
                                                        > > >
                                                        > >
                                                        >




                                                        --
                                                        -Nathan
                                                      • rtstofer
                                                        ... The regulator has a large pad on its bottom. How do I solder that thing? Toaster oven? A hot plate will work well if the circuit board is small enough
                                                        Message 27 of 30 , Sep 5, 2013
                                                        • 0 Attachment
                                                          --- In Electronics_101@yahoogroups.com, "Don" <DCFrench@...> wrote:
                                                          The regulator has a large pad on its bottom. How do I solder that thing? Toaster oven?

                                                          A hot plate will work well if the circuit board is small enough but a toaster oven probably works better.

                                                          http://www.rocketscream.com/shop/reflow-oven-controller-shield-arduino-compatible

                                                          http://www.youtube.com/watch?v=8j0impc6ebQ

                                                          I used a Black & Decker Infrawave toaster oven and just disconnected all the control parts, added a SSR and drove it with the rocketstream controller.

                                                          I added some high temp insulation in the cavities of the oven walls to help increase the rate of change of temperature.

                                                          There are many of these B&D Infrawave projects on the Internet.

                                                          Richard
                                                        • Stefan Trethan
                                                          I believe you do something wrong with eagle. Don t get me wrong, eagle is crap, but this I have done with it. You can adjust the via size and you can place a
                                                          Message 28 of 30 , Sep 5, 2013
                                                          • 0 Attachment
                                                            I believe you do something wrong with eagle.
                                                            Don't get me wrong, eagle is crap, but this I have done with it.

                                                            You can adjust the via size and you can place a square in the soldermask layer of the far side.
                                                            Don't ask me how, those are repressed memories.

                                                            You should want the vias regardless of soldering, because you need to transfer the heat the other other layer for dissipation.


                                                            ST


                                                            On Thu, Sep 5, 2013 at 7:15 PM, Don <DCFrench@...> wrote:
                                                            I was going to try that iron technique but got stymied at first when I could find no way to make a pad on the opposite side of the board.  Also, the smallest via I can make (with Eagle) is rather large - larger than the vias that the autorouter makes and certainly larger than the ones he made. I kind of hate to remove that much of the heat sink surface.  I think I solved the first problem by adding another regulator to the schematic but not wiring up any of its pins and then placing it on the opposite side of the board from the first one.  Maybe I can solve the second problem by filling the vias after the part is soldered on - or maybe they will fill in automatically.  Worth a try, I guess.

                                                            --- In Electronics_101@yahoogroups.com, "Don" <DCFrench@...> wrote:
                                                            >
                                                            > Thanks!  I just learned quite a lot from that crazy Aussie bloke.
                                                            >
                                                            >
                                                            > --- In Electronics_101@yahoogroups.com, Stefan Trethan <stefan_trethan@> wrote:
                                                            > >
                                                            > > Oven, hotplate, or hot air.
                                                            > >
                                                            > > That crazy aussie bloke has a video on youtube showing how you can do it
                                                            > > with just an iron if there are vias:
                                                            > > <http://www.youtube.com/watch?v=588iV07nEdM>
                                                            > >
                                                            > > ST
                                                            > >
                                                            > > On Thu, Sep 5, 2013 at 6:07 AM, Don <DCFrench@> wrote:
                                                            > >
                                                            > > > The regulator has a large pad on its bottom.  How do I solder that thing?
                                                            > > >  Toaster oven?
                                                            > > >
                                                            > > >
                                                            > > >
                                                            > >
                                                            >




                                                            ------------------------------------

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                                                          • Don
                                                            Not yet. I didn t have any 10 uF caps so I substituted 4.7uF ones, thinking that it wouldn t matter that much. So, as I have said in earlier posts, I will
                                                            Message 29 of 30 , Sep 6, 2013
                                                            • 0 Attachment
                                                              Not yet. I didn't have any 10 uF caps so I substituted 4.7uF ones, thinking that it wouldn't matter that much. So, as I have said in earlier posts, I will try that and a different inductor as soon as I get them. BTW, what does X5R and X7R mean?



                                                              --- In Electronics_101@yahoogroups.com, Nathan McCorkle <nmz787@...> wrote:
                                                              >
                                                              > Did you ever actually try the circuit with the datasheet-recommended
                                                              > configuration? It specifically mentions needing /at least/ 10uF, and
                                                              > mentions not to use tantalum, recommending ceramic X5R X7R caps instead.
                                                              >
                                                              >
                                                              > On Thu, Sep 5, 2013 at 10:15 AM, Don <DCFrench@...> wrote:
                                                              >
                                                              > > **
                                                              > >
                                                              > >
                                                              > > I was going to try that iron technique but got stymied at first when I
                                                              > > could find no way to make a pad on the opposite side of the board. Also,
                                                              > > the smallest via I can make (with Eagle) is rather large - larger than the
                                                              > > vias that the autorouter makes and certainly larger than the ones he made.
                                                              > > I kind of hate to remove that much of the heat sink surface. I think I
                                                              > > solved the first problem by adding another regulator to the schematic but
                                                              > > not wiring up any of its pins and then placing it on the opposite side of
                                                              > > the board from the first one. Maybe I can solve the second problem by
                                                              > > filling the vias after the part is soldered on - or maybe they will fill in
                                                              > > automatically. Worth a try, I guess.
                                                              > >
                                                              > >
                                                              > > --- In Electronics_101@yahoogroups.com, "Don" <DCFrench@> wrote:
                                                              > > >
                                                              > > > Thanks! I just learned quite a lot from that crazy Aussie bloke.
                                                              > > >
                                                              > > >
                                                              > > > --- In Electronics_101@yahoogroups.com, Stefan Trethan <stefan_trethan@>
                                                              > > wrote:
                                                              > > > >
                                                              > > > > Oven, hotplate, or hot air.
                                                              > > > >
                                                              > > > > That crazy aussie bloke has a video on youtube showing how you can do
                                                              > > it
                                                              > > > > with just an iron if there are vias:
                                                              > > > > <http://www.youtube.com/watch?v=588iV07nEdM>
                                                              > > > >
                                                              > > > > ST
                                                              > > > >
                                                              > > > > On Thu, Sep 5, 2013 at 6:07 AM, Don <DCFrench@> wrote:
                                                              > > > >
                                                              > > > > > The regulator has a large pad on its bottom. How do I solder that
                                                              > > thing?
                                                              > > > > > Toaster oven?
                                                              > > > > >
                                                              > > > > >
                                                              > > > > >
                                                              > > > >
                                                              > > >
                                                              > >
                                                              > >
                                                              > >
                                                              >
                                                              >
                                                              >
                                                              > --
                                                              > -Nathan
                                                              >
                                                            • Nathan McCorkle
                                                              ... 2nd hit on google for X5R http://www.edaboard.com/thread71490.html seems to be a temperature rating: X means minimum temperature range -55degC 5 means
                                                              Message 30 of 30 , Sep 6, 2013
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                                                                On Fri, Sep 6, 2013 at 10:10 AM, Don <DCFrench@...> wrote:
                                                                 

                                                                Not yet. I didn't have any 10 uF caps so I substituted 4.7uF ones, thinking that it wouldn't matter that much. So, as I have said in earlier posts, I will try that and a different inductor as soon as I get them. BTW, what does X5R and X7R mean? 


                                                                2nd hit on google for 'X5R'

                                                                seems to be a temperature rating:
                                                                "
                                                                X means minimum temperature range -55degC
                                                                5 means maximum temperature range +85degC
                                                                R means percentage of capacitance change permitted +/- 15%

                                                                X means minimum temperature range -55degC
                                                                7 means maximum temperature range +125degC
                                                                R means percentage of capacitance change permitted +/- 15%
                                                                "
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