06-01-2015 01:46 AM
In the KCU105 schematic a 2.2V zener diode is placed on the VCCINT_FPGA regulator output (0.95V).
I thought that the purpose of this Zener was to protect the FPGA in the event of the regulator output exceeding the absolute maximum VCCINT.
However, the absolute maximum VCCINT is 1.100V.
I can't see how the zener serves any purpose.
06-01-2015 03:59 AM
Please share the relevant part of that diagram which you are looking for review
06-01-2015 08:11 AM
I presume you mean D16.
Often, a diode or zener will be placed to protect the other devices.
Yes, 2.2v is beyond the absolute maximum Vccint ratings, but it will force the power supply to shut down (hopefully) before the FPGA device is destroyed. Or, it will be shattered by the power delivered to it, and leave behind evidence that the power supply had failed (often just knowing what went wrong is helpful).
Depending on the failure mode, and detection capabilities of the power supply, such means are suggested by the power vendor (they know their parts). I suspect that zener was selected by Maxim, for that POL device and its associated parts.