How to bring up FPGA board with short in the power rails.

Hi,

Debug steps

Check board for Solder Bridging (Specially near all power, ground pins).

Method -1

Force current and measure voltage(FCMV) which will help in finding the short.(source-measurement unit /Parametric-measurement unit/multimeter with high Resolution.

Method-2

You apply power, and look for a temperature rise on a specific component. It works quite well.

Method-3

Removing components.

1. List down the components on power rails(Regulators and passive components) try to suspect the component.(In my view i will suspect the 2.5V, 1.8V, 0.9V and 1.5V start heating DC-DC regulators->passive components ->FPGA)
2. If possible can we desolder the regulator and check.If short persist,
3. Try to do same for passive components on regulators and FPGA side.

Let me know if this has helped resolve the issue you are facing or if you need any further assistance.

Best Regards,

Anand Raj Shankar

(This message was posted on behalf of Intel Corporation)

Hi Anand,

Thank you for the message. What I have done so far:

Method -1. I have used Kelvin probe and the smallest resistance was detected below the FPGA on few decoupling capacitors .

it seems something like 10 mohm. (the ohm-meter has been zero with probes shorted)

Method -2 We have far end infrared camera and we are using regularly for this kind of issues.

The problem with this is that if we have +V ---resistor ---- short ---- GND the resistor is heating not the short.

In this particular case the main suspect so far is the FPGA (component or the soldering). The FPGA is heating a bit but not much.

if we apply 10Watts of the power input of this board I think something like 1, 2 Watts is dissipated by the FPGA the rest is dissipated mostly by the DC-DC regulators on this board (mainly +2.5V, +0.9V, +1.5V). Those heat a lot. At this point we have voltages on the rails like this :

+2.5V - 0.3V

+0.9V - 0.1V

+1.5V - 0.1V

Method - 3 Yes we have removed some of the components for the DC-DC regulators. Still short in the power rails. This is pretty big board and there are lot of the components.

I think we will try to use Method 1 a bit more and probably the next step is to un-solder the FPGA.

Any ideas will be greatly appreciated!

Best Regards

Dimitar

I guess you've checked that the FPGA hasn't been placed wrongly? I.e. rotated?

Hi Like,

Yes this has been done, and the chip is not rotated.

Thank you

Dimitar

Hi Dimitar,

May I request to check the FPGA is gone bad.

Regards,

RS