05-14-2014 02:15 PM
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?
05-14-2014 02:35 PM - edited 05-14-2014 02:39 PM
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...
05-14-2014 11:13 PM
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
06-05-2014 07:14 AM
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.
06-05-2014 07:33 AM
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).