Actions
Forum Thread Details
  • State Not Answered
  • Replies 8 replies
  • Subscribers 311 subscribers
  • Views 396 views
  • Users 0 members are here
Related

1V Power Rail Question

Former Member

I was looking at the 1.0V power section on the microzed (U17 and surrounding parts).

When the microzeds are in the Breakout Carrier and powered up, I am only seeing 0.2 Volts across C57. This is true for all my microzeds.

Shouldn't this supply be 1 Volt?

Cheers,
David

-EDIT-
1 of my 4 microzeds does in fact show 1.0V for this node.

Any ideas why the others do not?

  • 0

    Hi David.  Do you also see 0.2V if you do NOT have it plugged into the breakout carrier?  Is there a bit stream loaded in the FPGA?

    Do you have an oscilloscope you could put on the 1V during startup to see if it is coming up and turning off or if it isn't coming up at all?

    I haven't seen this before.  It could be a result of the input supply having insufficient power.  If the input supply is limiting, it could cause various rails to not start.  Are there any heavy loads on the carrier?  Are you trying to power it off a USB port?  If so, try powering it off a DC source or off say a USB cell phone charger.

    Thanks

    Chris

  • 0

    I measured the voltages at the output of each regulator for 4 uZeds. I tried to make a table, but I can't seem to format these messages.

    I'll summarize by saying that 1 uZed appeared healthy with the 1.0V supply measured as 1.0V. The 1.5V supply measured 1.49. The 1.8V supply measured 1.80V. The 3.3V supply measured 3.28V. This is with Vin=4.2V.

    3 other uZeds were virtually identical with: 1.0V supply measured 0.2V. 1.5V supply measured 1.5V. 1.8V supply measured 0.14V. 3.3V supply measured 3.28V. All with Vin=4.1V.

    So, in summary I have 1 good uZed and 3 uZeds that only have half the supplies operating properly.

    Any suggestions on what might be the root cause?

    Cheers,
    David

  • 0 in reply to ctammann

    Hi Chris,
    Good ideas.

    I've been running off an AC adapter rated at 2 Amps, not a USB port. I swapped it out for another 2A rated adapter and still see the same behavior.

    I removed the uZed from the carrier and powered it from the AC adapter. Now, none of the regulators are producing outputs, rather than half of them (see my other post). This is what I would expect, since they are enabled in series.

    I monitored the 1V power bus with a scope. Upon applying power, the voltage increases from 0V to 0.2V in about 200 microseconds and stays steady at 0.2V.

    Cheers,
    David

  • 0 in reply to Former Member

    So I removed the 1V power supply section on the microzed and drove it from an external, metered supply so that I could get an idea of how much current the board would draw.

    This did not shed much light on the problem. The board would gladly sink 3 Amps (applied for a couple hundred milliseconds). So I pulled the PHY chip (it's on the 1V supply bus) and still no joy.

    So the only chip left was of course the Zynq itself. I pulled it and the 1V bus is now happy. I don't see how this helps me much. What can I do but say that, out of the box, the Zynq chips draw large currents on the 1V bus?

    This really shakes my confidence in just about every aspect of my project.

    I did notice that all my microzeds have a bunch of re-work. You can tell from the solder flux residue at several places on the board.

    Why would brand new microzeds have a bunch of re-work? I'll post this as a separate thread.

    David

  • 0

    I'm checking into the rework now. All MicroZeds have a 1-year warranty. See http://microzed.org/policies. If the boards don't work properly out of the box, then please work with your local Avnet team to have an RMA issued and the boards replaced.

     

    I apologize for this issue. If you have any trouble with your RMA, please private message me.

    Bryan

  • 0

    Hi David,

    I echo Bryan's comments above.  An unconfigured MicroZed should NOT draw 3A on the core.  If that is your "good" board, you should RMA that one as well.  Bryan and I are talking about this issue as we speak.  I'll follow up with you directly shortly.

    Thanks

    Chris

  • 0 in reply to ctammann

    Thanks guys! I am grateful for your help.

    Cheers,
    David

  • 0 in reply to Former Member

    I've re-designed my power distribution and power sequencing, things look much better now.

    I believe that my reliability issues have been self-inflicted!

    Thanks for the help. I won't use the RMAs.

    Cheers,
    David