cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
Highlighted
Visitor
Visitor
10,258 Views
Registered: ‎06-07-2012

Virtex 5 XC5VFX130T - Excessive current draw on VCCAUX

Hi! I'm in the process of powering up my custom XC5VFX130T board. 1.0V for the VCCINT, 2.5V for the VCCAUX, and 3.3V for VCCO. The power supplies are turned on in the order recommended by the spec sheets. So VCCINT -> VCCAUX -> VCCO.

 

After all the power has been turned on, the 1.0V line is stable and draws 0.3 amps of current, the 3.3V line is stable and draws 0.05 amps of current, but the 2.5V line draws a whopping 1.4 amps of current, and the voltage drops to 2.1V.

 

I've done a preliminary inspection to exclude shorts as the problem, and now the only other circuitry connected to the 2.5V power supply is a NOR flash (properly connected) which draws less than a milliamp of current. Is 1.4amp @ 2.1V normal for this particular V5?

 

Thanks!!

0 Kudos
4 Replies
Highlighted
Scholar
Scholar
10,256 Views
Registered: ‎02-27-2008

No!

 

That is very very bad.

 

DS202 states 180mA max for the expected Vccaux.

 

What is getting hot?  With that much current, you should be able to find what is using that current easily.  As long as the FPGA does not get hotter than ~100C, it will not be damaged (by the heat).  If it is the FPGA device getting warm, then something on the Vccaux line has been damaged, or destroyed either prior to assembly, or during the assembly process.  Check the board Vccaux bypass capacitors.  An electrolytic capacitor in backwards may be responsible...

 

 

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
Highlighted
Xilinx Employee
Xilinx Employee
10,228 Views
Registered: ‎08-01-2012

One of the below also might cause  the problem

1) The power consumption in 2.55 supply rail is more than power supply/regulator rating

2) There could be some problem in board which associated with 2.5V suppl

________________________________________________

Please mark this post as an "Accept as solution" in case if it helped to resolve your query. So that it will help to other forum users to directly refer to the answer.

Give kudos to this post in case if you think the information is useful and reply oriented.

0 Kudos
Highlighted
Visitor
Visitor
10,105 Views
Registered: ‎06-07-2012

Hi Austin,

 

   We looked at the board with a thermal cam as it's powering up. Initially the edges of the FPGA is getting warm, and gradually the entire chip gets hot. I also attached a thermal couple to the top of the chip, the termperature seems to level off at around 40 degrees C, even when I'm loading a bitstream through the JTAG and have it run for a while.

 

  The bypass capacitors have all been checked for their polarity. 

 

Thanks!

James

0 Kudos
Highlighted
Scholar
Scholar
10,103 Views
Registered: ‎02-27-2008

James,

 

There is something wrong,  Iccaux is out of specification.  You should contact your authorized Xilinx distributor to arrange a warranty replacement (assumming you have never exceeded the absolute maximum ratings in the data sheet).

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
0 Kudos