Re: Input pins without Vcco supply-- Virtex-II

Austin,

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

"Austin Lesea" <[EMAIL PROTECTED]>
??????:[EMAIL PROTECTED]
> 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.
>
>
> Austin
>
> Jay wrote:
>
> > 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.
> >
> >
>