What digital bandwidth should I expect?

[fungus]

@jpa

It’s because of bad choice of ESD diodes on the digital inputs. They have too much capacitance and don’t really even limit the voltages.

There are suggestions for replacement diodes on these forums.

That sucks. They’re surface mount, too. Tricky for me to replace, even if we decide on a suitable replacement.

(I assume we’re talking about D5 in this image…)

@jpa

Myself I’ve been thinking about just taking those diodes out. They are 5V diodes, while the FPGA internally limits at 3.3V - therefore it should work just the same without the diodes and have much better digital bandwidth.

The FPGA has internal diodes or the FPGA is 3.3V and we’re hitting it with 5V?

Is there a suitable non-surface-mount (ie. easy to solder) diode I could put across the input connector for ESD protection? That way I could remove the internal one…

If not I might think about removing it. I’m not a very ESD-prone person (touch wood) and the contacts on the quad/probe are reasonably hard to touch in normal use.