Boot loop with USB power supply on DC barrel

I've encountered an power supply issue with microZed Soc. I'm trying to power the board using USB charger/Battery back. It worked fine through the UART USB port. But if I connect it through the DC barrel jack or VIN_HDR on the expansion header, the boot process will end up in a reset loop. Caps 212 217 218 are depopulated.

The reset happens after PL configuration and before entry to the OS. The multimeter show a significant voltage drop at the precise moment.

I've checked the schematics of the board design (rev F). Power through UART and VIN_HDR is no different. I've also included a polyzen on my carrier card.

Can someone shed some light on this?

Thanks!

0 jafoste4 over 5 years ago

Hello,
When you power your board via a wall jack does it operate correctly in both scenarios?
--Josh
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0 Former Member over 5 years ago in reply to jafoste4

If through an DC adapter that is fine. But I don't have access to that in the field. Only 5V battery pack or USB charger on a car.
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0 Former Member over 5 years ago

I'm suspecting some stray capacitance associated with Vin_HDR net. It's very reproducible.
Any idea how to solve it?
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0 Former Member over 5 years ago

OK, I did some testing with oscilloscope.
VIN_HDR during power on using a powerful adapter

With any USB charger (this one 3A rating) shows a voltage drop every 0.45s. Thus giving a boot loop

The same USB charger inserted to UART port shows a smooth power up. In fact, a 500mA regular USB port will also work.
I have two microzed and both of them experience the same problem. So I think it's a design issue. Can someone shed some light on this?
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0 Former Member over 5 years ago

Forum editor could not display my inserted image
three images in order described in the last comment
https://www.dropbox.com/s/o35ibola1dv10uq/T0000.PNG
https://www.dropbox.com/preview/Public/uZed_issues/TEK00006.PNG
https://www.dropbox.com/preview/Public/uZed_issues/TEK00009.PNG
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0 Former Member over 5 years ago

still no one? I've try power it using both side and then unplug the UART. It still resets.
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0 Former Member over 5 years ago

Can any FAE from zedboard help me on this issue? It's been months without reply.
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0 ctammann over 5 years ago

Hi, sorry for the late response here. Are you connected to the USB UART at the same time as power is being provided through Vin header? Is anything else being powered by Vin header on your carrier board? Adding back the bulk capacitance to the board may help with the voltage drop, which may be why the board is resetting. You could also try shorting D9. The UART should still be protected and you shouldn't have to worry about backfeed into the 5V from the barrel jack or carrier as long as the output voltage stays at 5V.
The first thing I would try is adding bulk capactiance to the Vin header node. Also verify that power is only coming from the Vin header and not from the UART port. The diodes D9 and D4 are there to protect the potential power sources, if you can assure you are only using one or the other then you can short these. Another option would be to short D9 and open D4 which would guarantee power from the DC source. Please give these a try and let me know if the problem persists.
Thanks
Chris
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