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Re: [Electronics_101] MAX712/713 charger

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  • Stefan Trethan
    On Sat, 4 Sep 2004 12:44:57 -0700 (PDT), paul thomas ... I have put the power parts close together with very short tracks, but i have no
    Message 1 of 184 , Sep 4, 2004
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      On Sat, 4 Sep 2004 12:44:57 -0700 (PDT), paul thomas <pbt1668@...>
      wrote:

      > Hi Stefan,
      > I know you are an, ‘elder member’ on this group, so
      > pardon me in advance for the stupid comments.
      > Concerning PCB layout, as this is a switcher you must
      > have a full ground plane for the board, the power
      > rails should be low impedance at 6A, and should also
      > be a plane. Concerning parts, the caps C5, and
      > possibly C4, C1 should be low ESR type, and the 100uH
      > coil should have self-resonance in terms of MHz as the
      > switcher IC is in terms of 100KHz. The diodes
      > (1N5820’s) should be mounted as close to the coil as
      > possible.
      > Lastly, most switchers will not work without a load,
      > maybe adding a 10 Ohm 1w across the load will help
      > debug the circuit.
      > Hope this helps,
      > Paul Thomas

      I have put the power parts close together with very short tracks, but i
      have no ground
      plane. I used power diodes out of other switching supplys.
      The switcher alone would work, but the max713 causes trouble.
      In the linear mode tried i finally got it to regulate the current.
      There was still a small 1Mhz oscillation but it seemed to work.
      As i would prefer a switcher i next tried the "switching mode" schematic
      on the last page of the datasheet. I thought if i can't stop the
      oscillations
      i will use it in a mode where the oscillations are wanted.
      It does not regulate well, and i don't know why so far.

      I must admit i'm a bit tired of it all, and i think maybe i should
      just make it linear and forget the switcher.
      I mean i can make a nice big heatsink in much less time than all this has
      taken
      already, and it isn't that much power....

      i'm building this charger because i want _reliable_ delta-u shutoff, and
      so far
      i can see none of that. If the charger isn't reliable then i can just as
      well continue
      to charge with constant current.

      thanks

      ST
    • Stefan Trethan
      On Sat, 4 Sep 2004 12:44:57 -0700 (PDT), paul thomas ... I have put the power parts close together with very short tracks, but i have no
      Message 184 of 184 , Sep 4, 2004
      • 0 Attachment
        On Sat, 4 Sep 2004 12:44:57 -0700 (PDT), paul thomas <pbt1668@...>
        wrote:

        > Hi Stefan,
        > I know you are an, ‘elder member’ on this group, so
        > pardon me in advance for the stupid comments.
        > Concerning PCB layout, as this is a switcher you must
        > have a full ground plane for the board, the power
        > rails should be low impedance at 6A, and should also
        > be a plane. Concerning parts, the caps C5, and
        > possibly C4, C1 should be low ESR type, and the 100uH
        > coil should have self-resonance in terms of MHz as the
        > switcher IC is in terms of 100KHz. The diodes
        > (1N5820’s) should be mounted as close to the coil as
        > possible.
        > Lastly, most switchers will not work without a load,
        > maybe adding a 10 Ohm 1w across the load will help
        > debug the circuit.
        > Hope this helps,
        > Paul Thomas

        I have put the power parts close together with very short tracks, but i
        have no ground
        plane. I used power diodes out of other switching supplys.
        The switcher alone would work, but the max713 causes trouble.
        In the linear mode tried i finally got it to regulate the current.
        There was still a small 1Mhz oscillation but it seemed to work.
        As i would prefer a switcher i next tried the "switching mode" schematic
        on the last page of the datasheet. I thought if i can't stop the
        oscillations
        i will use it in a mode where the oscillations are wanted.
        It does not regulate well, and i don't know why so far.

        I must admit i'm a bit tired of it all, and i think maybe i should
        just make it linear and forget the switcher.
        I mean i can make a nice big heatsink in much less time than all this has
        taken
        already, and it isn't that much power....

        i'm building this charger because i want _reliable_ delta-u shutoff, and
        so far
        i can see none of that. If the charger isn't reliable then i can just as
        well continue
        to charge with constant current.

        thanks

        ST
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