CMOD A-7

[anurag]

i have bought CMOD A-7. And if i define a pin as output and by mistake give it some input voltage(approx 3.3v) .will it damage the pin??if yes then please recommend a solution to avoid it.

 

[JColvin]

Hi @anurag,

Generally speaking, if you define a pin on an FPGA to be an output and then accidentally supply a matching input voltage (for example 3.3V output and supplying a 3.3V input) there should not be any problems. However, if your output was instead 0V and you accidentally gave it a 3.3V input voltage, you would likely damage the FPGA pin.

If you are concerned about this, what I would recommend to help mitigate this would be to implement some external resistors (in series) between the FPGA output pin and your input voltage. The Pmod port on the Cmod A7 already implements these series resistors for you, but the DIP pins do not. Realistically speaking, if you are aware of the potential issue of damaging the board, the knowledge of that should keep you from accidentally connecting incorrect voltages to one another. Otherwise, I might recommend using color coded wires to help ensure all of your signals go to the right places.

Let me know if you have any other questions.

Thanks,
JColvin

[xc6lx45]

On 1/16/2018 at 9:30 AM, anurag said:

... define a pin as output and by mistake give it some input voltage(approx 3.3v) .will it damage the pin??...

Hi,

have a look at this on the Xilinx forum:
https://www.xilinx.com/support/answers/23277.html

"... where the various I/Os of the different Virtex/Spartan families have been shorted to Ground or VCC with outputs programmed for strongest drive strength..This condition has been maintained over days and weeks with no latent damage seen"
Well, the article was written well before 28 nm came out, but it's up to interpretation anyway since they don't promise anything.

I'd suggest to use common sense, and not lose sleep over a $50 component. Save that for the $3500 board that has +12V 3A on FMC connectors... a slipped probe will blow the whole IO bank. Seen that happen and no, it wasn't me...

BTW, note that the VCC pin is +5V. With that, I'd be a little more careful than regular +3.3V.