# How to vary the supply voltage for Xilinx Virtex-5 FPGA ML501, ML506, and ML510 boards?

I'm trying to do an experiment to see how different supply voltages affect the frequency of ring oscillator and the reliability of SRAM cells. I have access to a couple of Xilinx Virtex-5 boards, namely, ML501, ML506, and ML510. I have tried to search the web, but so far I haven't found anything useful. I have some experiences with FPGA design, but I have never tried to change the supply voltage before. So I'm really clueless on how to start. Can someone (who have done similar projects) please tell me how to vary the supply voltage of those FPGA boards?

• Have you considered using an external power supply? – Ignacio Vazquez-Abrams Nov 6 '13 at 0:04
• Yeah just bodge in an LM317 or some sort... fairchildsemi.com/ds/LM/LM317.pdf – Dzarda Nov 6 '13 at 0:06
• I haven't considered using an external power supply because it seems too risky. The boards I have are very expensive, and I don't want to damage them by accident. What I am looking for is a voltage-regulator module that I can instantiate in my design. – abc Nov 6 '13 at 0:19
• Ah hahaha. No, you're not going to be able to instantiate anything like that. That's not how FPGAs work. The only way to mess with the VCCINT voltage is by actually messing with the voltage externally. – alex.forencich Nov 6 '13 at 6:16
• @Dzarda That's a really bad idea. FPGAs need something like 1.0 volts at 10 to 20 amps or more. An LM317 is not the right tool for the job. However, the board probably has an adjustable DC-DC converter with remote sensing on it already, all you need to do is change the voltage set resistor(s) and you're good to go – alex.forencich Nov 6 '13 at 6:20

• @alex.forencich, IMO adding a pot makes things a little riskier on the bench. If this was $100 worth of hardware, I'd do it, but with$1K of hardware I'd try to eliminate any possible chance of error. – mng Nov 6 '13 at 14:40