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The PG output is open-drain, which is why we have the pull-up. The weak pull-down was added to more quickly shut down the circuitry in a power-off event. That is why you see the voltage divider. This circuit originated on MicroZed, and PicoZed inherited the design.
The pull-up value has gone through some iterations due to another issue on the board that was resolved. You can read about this in the MicroZed Rev G errata, Issue 3.3.
On MicroZed Revisions F-05 and earlier, an issue was identified where this signal was affected by backfeed
from the VTT regulator. Resistor R35 was changed from 1.0K to 1.5K on Revision F-06 to accommodate
this other issue. Revision G maintained this 1.5K resistor for consistency.
The VTT backfeed problem was corrected on Revision G, so R35 could be replaced with 1.0K-ohm without
Therefore, I think you have two options:
- Reduce the resistance on the R67 pull-up which will raise the output voltage on PG_1V8. This maintains the shutdown behavior as designed.
- Remove the pull-down, which also raises the output voltage on PG_1V8. However, the customer is responsible for determining if the shutdown behavior is acceptable, meets eFuse requirements, etc.