SLUUBT5C November 2018 – June 2021 BQ40Z80
When a pin is selected as PDSG to control pre-discharge, the associated pin (except for LEDCNTLA) is used to drive an external NFET, which pulls down the PDSG PFET gate. The exception is if the PDSG functionality is selected using the LEDCNTLA pin (RL0, pin 20), which has an internal high-voltage drive capability and can drive the PFET gate directly (in which case the polarity of the pin signal changes). The NFET should have a pulldown resistor on its gate to keep it turned off in SHUTDOWN mode, because in SHUTDOWN mode, most pins are in HIGH-Z mode.
The PFET implements a PRE-DISCHARGE mode to slowly charge up the load before the DSG FET is turned on. The pullup resistor from the PFET gate to PACK+ ensures that the PFET gate turns off when the gate is in SHUTDOWN.