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

Jim

"Austin Lesea" <austin@xilinx.com> wrote in message 
news:cnd7kg$iv81@cliff.xsj.xilinx.com...
> Jim,
>
> That sounds like a complete electrical overstress of Vcco (basically, 
> complete oxide and/or junction failure).
>
> That is usually something caused by a power supply grossly overshooting on 
> turn on (as in way beyond the abs max ratings), or momentary negative 
> voltage being forced on the IO pins, or the Vcco supply (as in a momentary 
> short to -48V -- always sure and sudden death!).
>
> Austin
>
> Jim wrote:
>> Part failure as in 3.3v sucking mucho current > 5 amps, when normally the
>> module takes less than 100ma idle. When problems began, measured 2 ohms 
>> from
>> 3.3v to gnd. 30ohm from 1.5v to gnd.
>>
>> Haven't done a full analysis yet, but the only active 3.3v parts on the
>> board are the virtexII xc2v40, xcf02s, 2 quickswitch idtqs3r861
>>
>> Thanks for replying, will post more when more info is available.
>> Jim
>>
>>
>> "Austin Lesea" <austin@xilinx.com> wrote in message
>> news:cnb541$kht1@cliff.xsj.xilinx.com...
>>
>>>Jim,
>>>
>>>See below,
>>>
>>>Austin
>>>
>>>Jim wrote:
>>>
>>>
>>>>Help,
>>>>I've been trying to find a definitive answer to this question. Can I
>>
>> connect
>>
>>>>Virtex II pins configured as pure outputs (LVCMOS33 or LVTTL) directly
>>
>> to 5v
>>
>>>>LSTTL, ACT, or FCT INPUTS  without any resistors and not risk any damage
>>
>> ?
>>
>>>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.
>>>
>>>>I've used the quickswitch design from the appnotes for my bidirectional
>>>>pins, and 175 ohm series resistors for 5v TTL inputs to the Virtex II,
>>
>> but I
>>
>>>>tied  the fpga outputs directly to 5v input logic pins and now I think I
>>>>have a Virtex II part failure.
>>>
>>>Unlikely this is the cause.  Unless the inputs can behave as outputs?
>>>Check during power ON? power OFF?
>>>
>>>>Any feedback greatly appreciated.
>>>
>>>When you say a "part failure" what kind of failure?
>>>
>>>>Thanks
>>>>Jim
>>>>
>>>>
>>
>> 

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!).

Austin

Jim wrote:
> 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
> 3.3v to gnd. 30ohm from 1.5v to gnd.
> 
> 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
> 
> 
> "Austin Lesea" <austin@xilinx.com> wrote in message
> news:cnb541$kht1@cliff.xsj.xilinx.com...
> 
>>Jim,
>>
>>See below,
>>
>>Austin
>>
>>Jim wrote:
>>
>>
>>>Help,
>>>I've been trying to find a definitive answer to this question. Can I
> 
> connect
> 
>>>Virtex II pins configured as pure outputs (LVCMOS33 or LVTTL) directly
> 
> to 5v
> 
>>>LSTTL, ACT, or FCT INPUTS  without any resistors and not risk any damage
> 
> ?
> 
>>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.
>>
>>>I've used the quickswitch design from the appnotes for my bidirectional
>>>pins, and 175 ohm series resistors for 5v TTL inputs to the Virtex II,
> 
> but I
> 
>>>tied  the fpga outputs directly to 5v input logic pins and now I think I
>>>have a Virtex II part failure.
>>
>>Unlikely this is the cause.  Unless the inputs can behave as outputs?
>>Check during power ON? power OFF?
>>
>>>Any feedback greatly appreciated.
>>
>>When you say a "part failure" what kind of failure?
>>
>>>Thanks
>>>Jim
>>>
>>>
> 
> 
> 

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
3.3v to gnd. 30ohm from 1.5v to gnd.

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


"Austin Lesea" <austin@xilinx.com> wrote in message
news:cnb541$kht1@cliff.xsj.xilinx.com...
> Jim,
>
> See below,
>
> Austin
>
> Jim wrote:
>
> > Help,
> > I've been trying to find a definitive answer to this question. Can I
connect
> > Virtex II pins configured as pure outputs (LVCMOS33 or LVTTL) directly
to 5v
> > LSTTL, ACT, or FCT INPUTS  without any resistors and not risk any damage
?
> 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.
> >
> > I've used the quickswitch design from the appnotes for my bidirectional
> > pins, and 175 ohm series resistors for 5v TTL inputs to the Virtex II,
but I
> > tied  the fpga outputs directly to 5v input logic pins and now I think I
> > have a Virtex II part failure.
> Unlikely this is the cause.  Unless the inputs can behave as outputs?
> Check during power ON? power OFF?
> >
> > Any feedback greatly appreciated.
> When you say a "part failure" what kind of failure?
> >
> > Thanks
> > Jim
> >
> >

Jim,

See below,

Austin

Jim wrote:

> Help,
> I've been trying to find a definitive answer to this question. Can I connect
> Virtex II pins configured as pure outputs (LVCMOS33 or LVTTL) directly to 5v
> LSTTL, ACT, or FCT INPUTS  without any resistors and not risk any damage ?
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.
> 
> I've used the quickswitch design from the appnotes for my bidirectional
> pins, and 175 ohm series resistors for 5v TTL inputs to the Virtex II, but I
> tied  the fpga outputs directly to 5v input logic pins and now I think I
> have a Virtex II part failure.
Unlikely this is the cause.  Unless the inputs can behave as outputs? 
Check during power ON? power OFF?
> 
> Any feedback greatly appreciated.
When you say a "part failure" what kind of failure?
> 
> Thanks
> Jim
> 
> 

Help,
I've been trying to find a definitive answer to this question. Can I connect
Virtex II pins configured as pure outputs (LVCMOS33 or LVTTL) directly to 5v
LSTTL, ACT, or FCT INPUTS  without any resistors and not risk any damage ?

I've used the quickswitch design from the appnotes for my bidirectional
pins, and 175 ohm series resistors for 5v TTL inputs to the Virtex II, but I
tied  the fpga outputs directly to 5v input logic pins and now I think I
have a Virtex II part failure.

Any feedback greatly appreciated.

Thanks
Jim