FPGA bank voltage change on the fly...

[bkjobs2006]

Hi Gurus,

Is it OK to change the bank voltage of a FPGA (say 3.3V to 1.8V), on the fly?
The application needs the IO voltages to be changed from one level to another (say 3.3V to 1.8V) and viceversa. To make this happen, the corresponding bank voltages also has to be set accordingly.

If so, any ideas on how this can be implemented? Any thoughts on power switches?

Thanks in advance,
bkjobs

 

[mersault]

do you have a FPGA development kit? (like spartan3e, for example).
If the answer is yes, maybe you could implement your variable voltage bank using the dac conversor attached to the platform.

another solution is to set one pin to 1.8 V and another with 3.3 V, then program a module that control what output will have a "one" in certain moment, and then add this two voltages with an opamp.

 

[JacquesKleynhans]

Hi I am using a Actel FPGA, I'm setting my banks directly to 1.5, 1.8, 2.8 and 3.3 using the allocated pins on the banks.

J

 

[zape]

If you are changing bank voltages I presume you will be changing also de I//O standard, so a new FPGA configuration should be loaded.

I recommend you to have a unique FPGA design with all the required interfaces plus external switches. This is an easy way for modifying the logical voltage levels used.

 

[FvM]

so a new FPGA configuration should be loaded

Not generally necessary. An I/O voltage in pin configuration is mainly a calculation rule to set drive strengths, it doesn't actually change configuration data as long as you keep the basic pin type and the relative drive strength.

 

[permute]

depending on the application, you might also be able to use open-drain logic.