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Re: [nslu2-linux] Anyone know how the slug 5V to 3.3V power conversion works?

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  • michael taylor
    ... Where are you measuring that power rail? What is the wall-wart power supply voltage unloaded (not plugged into the board) and loaded (plugged into the
    Message 1 of 9 , Nov 1, 2007
      On 11/1/07, Rod Whitby <rod@...> wrote:
      > I have a slug which is not working (symptom is a short blink on the
      > power led on power-up, and then nothing on any leds after that, and
      > nothing on the serial console), and I'm measuring less than 1V on the
      > 3.3V power rail.

      Where are you measuring that power rail?

      What is the wall-wart power supply voltage unloaded (not plugged into
      the board) and loaded (plugged into the board, measure from the power
      plug on board is easiest)?

      Some quick measurements I just did.

      Wall wart,
      unloaded: 5.12 V
      loaded: 5.08 V

      C45: 5.08V (near RAM)
      C21: 3.3V (near Realtek Ethernet chip)
      C146: 3.xx V (underside, near power switch)
      D13: 3.0V (anode) 2.4 (or 2.5)V (cathode) (underside near 4 LEDs and
      Real-Time-Clock)


      > Does anyone have any details on the slug's internal power conversion
      > circuitry? I'd like to work out what has failed ...

      I assume you have identified U16 as the power management IC, Feeling
      Technology's FP5452
      with under-voltage lock out, and short circuit protection.

      FP5452 datasheet <http://www.dianyuan.com/bbs/u/46/1160442105.pdf>

      Don't know if that helps at all.
    • MIKi
      An step-down voltage regulator should have a coil, a big capacitor and a small black integrated circuit. As I see the picture on the main page here, the
      Message 2 of 9 , Nov 1, 2007
        An " step-down " voltage regulator should have a coil, a big capacitor
        and a small black integrated circuit.
        As I see the picture on the main page here, the slug should have two
        regulator. The first is left from the memory-s, the second is on the
        bottom close to the right corner.
      • Rod Whitby
        ... Any chance you could draw the circuit diagram for me (and explain it s operation), so I can match it to the components on the slug and start measuring some
        Message 3 of 9 , Nov 1, 2007
          MIKi wrote:
          > An " step-down " voltage regulator should have a coil, a big capacitor
          > and a small black integrated circuit.
          > As I see the picture on the main page here, the slug should have two
          > regulator. The first is left from the memory-s, the second is on the
          > bottom close to the right corner.

          Any chance you could draw the circuit diagram for me (and explain it's
          operation), so I can match it to the components on the slug and start
          measuring some voltages?

          Hi-res photos of the PCB (including boards will all components removed)
          can be found at:

          http://www.nslu2-linux.org/gallery/nslu2_pcbs

          -- Rod
        • MIKi
          ... This circuits are very simples, at home visual inspection usable only. Because of the converters working on higher frequencies, You cant measure or check
          Message 4 of 9 , Nov 1, 2007
            > Any chance you could draw the circuit diagram for me (and explain it's
            > operation), so I can match it to the components on the slug and start
            > measuring some voltages?
            >

            This circuits are very simples, at home visual inspection usable only.
            Because of the converters working on higher frequencies, You cant
            measure or check anything on your desk : (
          • MIKi
            Perhaps this values should be OK, but as You see w/o more information nobody can say anything about your voltages ... : (
            Message 5 of 9 , Nov 2, 2007
              Perhaps this values should be OK, but as You see w/o more information
              nobody can say anything about your voltages ... : (
            • Phil Endecott
              ... Hi Rod, I know exactly how it works. Do you have access to an oscilloscope? Phil. (If you cc: me in your reply, I ll see it sooner; I m subscribed to the
              Message 6 of 9 , Nov 2, 2007
                Rod Whitby wrote:
                > I have a slug which is not working (symptom is a short blink on the
                > power led on power-up, and then nothing on any leds after that, and
                > nothing on the serial console), and I'm measuring less than 1V on the
                > 3.3V power rail.
                >
                > Does anyone have any details on the slug's internal power conversion
                > circuitry? I'd like to work out what has failed ...


                Hi Rod,

                I know exactly how it works. Do you have access to an oscilloscope?


                Phil.

                (If you cc: me in your reply, I'll see it sooner; I'm subscribed to the digest.)
              • sdm485
                The FP5452 datasheet has an application note that should provide the basic design. I just took a look at one of my units and capacitor C45 is bulging in the
                Message 7 of 9 , Nov 2, 2007
                  The FP5452 datasheet has an application note that should provide the
                  basic design. I just took a look at one of my units and capacitor C45
                  is bulging in the same way as ones on a few failed motherboards I
                  fixed a while ago. It is possible that you have the same problem.
                  There was quite a scandal about it a few years back. If it turns out
                  to be a problem, you need a low ESR device in that location and
                  replacing C48 as well would be a good idea.

                  Steve



                  --- In nslu2-linux@yahoogroups.com, Rod Whitby <rod@...> wrote:
                  >
                  > I have a slug which is not working (symptom is a short blink on the
                  > power led on power-up, and then nothing on any leds after that, and
                  > nothing on the serial console), and I'm measuring less than 1V on the
                  > 3.3V power rail.
                  >
                  > Does anyone have any details on the slug's internal power conversion
                  > circuitry? I'd like to work out what has failed ...
                  >
                  > -- Rod
                  >
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