Has anybody used these?
We have two FPGAs on a board, a Zynq and an Artix7. We want to use the internal ADCs to read chip temperatures. We have been advised to ground the temp sense diode pins DXP and DXN "if they are not being used".
Unless the XADC has a separate temp sense diode, seems to me that shorting the external diode pins might kill our ability to acquire temperature internally.
I don't see any big downside to not grounding those pins.
After too much research, it seems that there are independent temp sensors, the external-pin one and another inside the XADC.
And they recommend grounding DXP and DXN to improve the ESD rating. IIRC there's no functional issue caused by leaving them open.
Regards, Allan
Right, the esd thing makes no sense at all.
Why do you say it makes no sense? A lot of devices have an improved ESD rating when their more sensitive pins are connected to low impedance sources (as opposed to being open).
Of course, if those pins are on a via-less pad under a BGA on a PCB with good planes, the difference may be hard to measure.
Regards, Allan
Do you ground every unused pin on every FPGA?
Of course not, but I do ground pins that the manufacturer says to ground.
Last century (using QFP packages) I would sometimes ground extra IO pins to help with ground bounce on IO banks that had more O than I.
Allan
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