Honored Contributor
Honored ContributorHi,
how do you limit the current to 2mA? I mean, if there's a series resistance to limit the current, the voltage will never go to 10V, as the input protection diodes of the device would surely require a lot more current to do so. Anyway, you're making assumptions about the input protection diodes, and you're trying to operate the device outside of it's operating range, so I would not count on reliability. For a hobby project I'd say it's fine, for a product I'd say it might be dangerous. Maybe you should contact Altera and ask them directly about their opinion. Do you at least have space to add some Schottky diodes? Since you're current is limited to 2mA, very small (I mean physically small) diodes would already protect the FPGA quite well, without relying on the FPGA's protection diodes. If you look at figure 3-1 in section "MAX 10 FPGA Configuration Design Guidelines" of the MAX 10 device handbook, they recommend quite rigid protection scheme of the JTAG input pins. That leads me to the conclusion that in doubt better use additional external diodes. Maybe I'm just over-cautious, though. Best regards, GooGooCluster
