Regulator failure on 1V8 from ADP5052ACPZ-R7 on Pt board?

General
1

I just went to plug in my Alchitry Pt board, Fan Board and FT board and it suddenly stopped working. I think I may have plugged the Ft USB in first. I heard the fan spin up and saw the green LEDs light up. Then I went to plug in the second USB cable (for the Pt I think) and just as I touched the connector and before I even got the connector plugged in, suddenly the LEDs all went off and the fan stopped.

It will no longer power on.

I think the power supply has failed.

Here’s what I have so far:

I’m looking around U4 part ADP5052ACPZ-R7.

I see VREG at 5V on pin 44.

I see that pin 26,27 (SW2) is driving a switching signal to L2, and the output of L2 is at 1V as expected.

I then see that this should feed pin 48 (EN3), which seems to be working, as I see a switching signal at pin 3 (SW3) driving in to L3. But I don’t see any output at the output of L3. I expect 1.8V.

The signal at SW3 also looks intermittent.

I think I should start by ordering another board ASAP.

Any suggestions on how to debug/repair this?

Any idea what could have gone wrong?

Thanks!

Signal at input of L2:

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image907×737 67.3 KB

Signal at input of L3:

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image907×759 52.8 KB

Output of L3:

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image924×745 50.6 KB

It seems this is ramping up but then stops before it even reaches 1.8V… could this indicate a short in the 1.8V load and a protection behavior by U4?

2

Here’s me hoping this was a one-off failure!

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3

This is strange. I’d like to take a look at the board. I’ll send you a RMA for it.

It shouldn’t matter if you plug in the Ft or Pt first.

4

Okay. I haven’t done any destructive work trying to fix it yet, so I’ll hold off on any further testing and get it back to you when I’m back on Monday.

To be clear: I didn’t actually manage to plug the second USB cable in. It failed as soon as the cable shield made contact to the connector.

I don’t see anything in the schematic or layout that could explain this, so I agree, this is strange.

And it doesn’t seem likely that this was an ESD event because the first cable was already connected to the same PC, so any static charge would have been equalized.

5

I’d agree from what you said ESD doesn’t sound likely unless it hit somewhere other than the connector (it is an exposed PCB after all).

I’ll take a look and report back once we receive your board.