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Altera_Forum
Honored Contributor I
1,390 Views

Stratix5 - VCCCORE to GND resistance is almost 0 ohm

Hi, 

 

We have designed a PCB for the Stratix V device.  

We found the resistance between VCCCORE and GND is almost 0 ohm, thus we never powered it up. 

 

 

To clarify the problem, FPGA was disassembled the from the PCB. We found that the resistance between VCCCORE and GND is 0.02ohm on the FPGA itself. 

 

 

Is it normal? Can we continue to power up the PCB? 

 

 

Thanks in advance.
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3 Replies
Altera_Forum
Honored Contributor I
57 Views

Hi, 

 

1.Are you sure you got 0.02 ohm after probing FPGA vcc core and Gnd?  

Re-check you may be probing some of other GND pins instead of Vcc core because of device pitch. 

2.Have you checked the board ?(Converters, regulator & passive components in the path) 

 

It is a short as per your value. 

 

Best Regards, 

Anand Raj Shankar 

(This message was posted on behalf of Intel Corporation)
Altera_Forum
Honored Contributor I
57 Views

Hi, Anand, 

 

1. Yes, I am sure that correct pins are probed. 

 

2. 0.02 ohm is the value after Stratix V has been removed from the PCB. We probe on the Stratix V without PCB. 

 

Today, we use X-ray to analyze another PCB with a mounted Stratix V on it. We found that the DNU pin is shorted to GND, because of the SMT process. 

 

The "Pin Connection Guidelines" says "DNU: Do not connect to power, ground or any other signal. These pins must be left floating. " 

 

In fact, those PCBs are never powered up, because of the short problem. 

 

Is there possible that the FPGA is damaged when SMT-process short the DNU to GND?  

 

Many Thanks, 

Vina
Altera_Forum
Honored Contributor I
57 Views

Hi Vina, 

 

1.Do you have any spare FPGA so that you can probe and compare.  

If you are sure on the 0.02 ohm, than FPGA may be damaged.  

or You can submit a request to mysupport for FA(failure analysis). 

 

2.If board is not powered ON than FPGA may be fine. 

 

Best Regards, 

Anand Raj Shankar 

(This message was posted on behalf of Intel Corporation)