Input pins without Vcco supply-- Virtex-II

Hi all, The factory have made some mistakes when they had our V-II pcb board manufactured and assembled. and we found only the Vccint, Vccaux and Vcco4 is available for the FPGAs. To save time, we still want to do some debugging on this board before we can get our new board. Thanks god that with these 3 Vcc supplies we can download our design through JTAG, and later I found input signals of other banks without Vcco still can be used.(at least the GCLK, I've not tried other pins yet). so my question is: can anyone confirm that I really can use the input pins without Vcco. and how about its Electrical Characteristics, ?V tolerant etc.

Reply to
Jay
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Jay,

By using the banks that are unpowered as inputs, you are in effect powering up the bankl by reverse biasing the protection structures (diodes) that are part of the pmos output transistor stack (basically, there is no separate diode, it is the junction of the pmos transistor itself).

That said, the bank requires ~ 2mA to power on (as long as it doesn't have to drive anything) so a bunch of inputs toggling effectively powers up the bank....

Doesn't hurt anything at all. Can't say that we meet all specifications for timing, etc. but you are certainly able to function.

In fact, the clock inputs are no different than any others, so you are powering up the bank from those alone.

If you really want to power up the bank for test reasons, I would program an output to be a "1" with the PCI IO standard (one of the strongest) and themn connect that pin to 3.3V. That is good for ~ 60 mA of IO current without concern. Need more outputs? Parallel up a bunch of IOs as "1" to 3.3V.

Aust> Hi all,

Reply to
Austin Lesea

Austin,

Thanks your answer. It sounds good! That means we can use IO pins as power supply instead of Vcco.

"Austin Lesea" ??????:bq2hma$ snipped-for-privacy@cliff.xsj.xilinx.com...

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Reply to
Jay

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