Do the power supply designs for MicroZed and PicoZed meet the requirements described in Xilinx Answer Record #65240? Here is the link:
Design Advisory for Zynq-7000 AP SoC: Power-On/-Off Sequence Requirements for PS eFUSE Integrity
I think the power supply design handles the power-on sequence very well. But I'm not sure about the power-off sequence. MicroZed uses the TLV62130RGT regulator, which has a minimum supply voltage of 3V. I am concerned that the Power Good (PG) output is not controlled when the input voltage is less than 3V. The TLV62130RGT regulator also has a floating PG output that complicates analysis. Please look at the following application report from Texas Instruments regarding the PG output of the TLV62130 and TLV62130A:
It says "The TPS62130A device differs from the TPS62130 device only in how the PG (power good) pin is controlled when the device is disabled, in UVLO, or in thermal shutdown. The TPS62130A holds the PG pin low during these conditions, while the TPS62130 sets the PG pin high impedance (floating). This is typically only a concern in a system that uses multiple voltage rails or where an output discharge function is required".
Section 9.3.3 of the TLV62130/A data sheet says "Vin must remain present for the PG pin to stay Low". I think that implies it needs to be above 3V.
One solution I found is to use a supervisor chip that operates at 0.80V or less. It needs to monitor both the 1.0V rail as well as VCCO_MIO0 (often 3.3V). Xilinx has produced a PDF showing one example of a PS_POR_B Supervisor Circuit that ensures the eFuses will not be damaged. Here is the link:
In the MicroZed and PicoZed power supplies, how is it guaranteed that the 1.0V rail has not fallen to 0.80V while the 3.3V rail is above 0.9V? It doesn't look like the 1.0V, 1.8V, and 3.3V voltages are present on the 100-pin connectors, so I don't see a way for the user to monitor them and drive PG_MODULE appropriately. Vin can be monitored, but Vin could potentially drop before the outputs of the switchers have decayed. I suppose the user's circuitry could control Vin and the PG_MODULE signal. I think that would be reliable. Thank you in advance for evaluating my question.