On PicoZed Rev. E, the "Carrier RESET" is implemented like this:
PS_SRST_B is connected directly to ZynQ-7000 PS_SRST_B_501.
The problem is that if I would like to use this signal from my carrier board e.g. by connecting a push button between CARRIER_SRST# and ground, the voltage level on PS_SRST_B may not be low enough to actually RESET the ZynQ chip.
If I connect CARRIER_SRST# to ground, the current flows through the Q6 diode, and the diode forward voltage is seen on PS_SRST_B. The Q6 datasheet doesn't give an explicit answer to this, because the current through 10K resistor is really low (the graph is drawn only to 1mA minimum, forward voltage is about 0.55V at 25 celsius). According to Xilinx ds187 the maximum low level limit for ZynQ-7000 PS_SRST_B_501 (LVCMOS18) is 35% of 1.8V i.e. ~ 0.63V.
Can you guarantee, that the Zynq chip is reset by pulling CARRIER_SRST# low over the entire specified operational temperature range, and in spite of component-to-component variance?