Help with Virtex II and 5v TTL

Jim,

See below,

Aust> Help,

Yes (you can connect directly a 3.3V output to a 5V input). It is the reverse that you can not do without a resistor.

Unlikely this is the cause. Unless the inputs can behave as outputs? Check during power ON? power OFF?

When you say a "part failure" what kind of failure?

Part failure as in 3.3v sucking mucho current > 5 amps, when normally the module takes less than 100ma idle. When problems began, measured 2 ohms from

Haven't done a full analysis yet, but the only active 3.3v parts on the board are the virtexII xc2v40, xcf02s, 2 quickswitch idtqs3r861

Thanks for replying, will post more when more info is available. Jim

connect

to 5v

but I

Jim,

That sounds like a complete electrical overstress of Vcco (basically, complete oxide and/or junction failure).

That is usually something caused by a power supply grossly overshooting on turn on (as in way beyond the abs max ratings), or momentary negative voltage being forced on the IO pins, or the Vcco supply (as in a momentary short to -48V -- always sure and sudden death!).

Aust> Part failure as in 3.3v sucking mucho current > 5 amps, when normally the

Thanks Austin, will check the power supplies more carefully and post back when I have more info.

Jim