Power Good LED (LD11) Blinking on Arty A7-35T

[Bruce_W]

Good Afternoon Sir,
                                 We have an Arty A7-35T. Our board is not powering up properly.

The issue is the Board is not powering up when connected  to PC but does when connected to a Power Brick(Power Adapter).

To be more specific the Power Good LED on the FPGA (LD11) keeps blinking when connected to the PC but works fine when connected to an Power brick(Power Adapter).

We tried all the possible troubleshooting like try changing the cable, PC but the result is the same.

Where could the issue be? Is it possible to rectify? We request you please assist us to overcome this issue. Hoping to hear from you soon

 

Thanks & Regards
Bruce

[Bianca]

Hi @Bruce_W,

If the LED is blinking it means that the 3.3V power supply is not working constantly. I don't know if with a multimeter we can see the behavior, probably just with a scope, but if you have a voltmeter/multimeter, please try to measure the voltages on, C208, C176 (or C177) and C178 (or C179) while you power the board from the PC with the USB cable. It will average the values, but if the power supply is that unsteady, you might be able to see some fluctuations. There's an overcurrent protection IC on the path when using USB power. I suspect that to be the cause of the problem.

 

Bianca

[Bruce_W]

Hi @Bianca,

               As per your advice, I went on and measured the values of C176,C177,C178,C179 by powering the FPGA via USB. The values were as follows C176,C177=5.10V & C178,C179=0.00v to 0.15v (the volt kept fluctuating). In case of C208 I couldn't find it on the board. I can check its value if the location is provided for the same. What are the possible fixes for this issue? Also when connected to a power brick I read the following readings for the capacitors C176,C177=4.17V & C178,C179=3.29V.

Thanks & Regards
Bruce

[Bianca]

Hi Bruce,

It's ok, You confirmed what I thought the issue was... There is something, and I suspect the current protection (IC13), that is defective and is putting the Dialog power supply under stress. 

I will send you a private message regarding the purchase details of the board, to see if it's still under warranty. If it's not. I would suggest replacing IC13 (NCP380HMUAJAATBG) and try again; if you can't find the part on stock, you can also try to bypass it. But this will leave the board exposed to short circuits and overcurrent. You can check the schematic here.

Regards,

Bianca