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Old 11-28-2007, 12:47 AM
Peter Alfke
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Default Re: Xilinx IO leakage when not powered

On Nov 27, 3:38 pm, [email protected] wrote:
> HI
> I have a Xilinx Spartan3e IO pin connected to a system bus signal. The
> system bus signal can be active (3.3v/0v) even when the Spartan device
> is powered off. When the signal is at 3.3, I suspect the ESD
> protection diode between pad and VCCO on the Spartan IOB is going to
> turn on. Does anybody know what would be the current drawn?
> -Dipankar

Get a multimeter and measure the current!
I would also observe the Vcco (I/O supply voltage) while the pin is
being driven High.
Most devices have a strong diode between any I/O pin and its Vcco
supply pin.
Some devices claim to be "hot pluggable" and avoid this diode-clamping

Peter Alfke, Xilinx Applications
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