ZHCSF60K June 2016 – July 2020 BQ77904 , BQ77905
PRODUCTION DATA
When the CHG driver is off, CHG is pulled to VSS, the PACK– terminal can be pullup to the PACK+ level when a load is connected. This can put the gate-source voltage above the absolute max of the MOSFET rating. Hence, it is common to place a Zener diode across the CHG FET’s gate-source to protect the CHG FET. Additional components are added when a Zener is used to limit current going into the CHG pin, as well as reducing the impact on rise time. See Figure 9-4 for details.
Figure 9-4 Protect CHG FET from a High Voltage on PACK–
Figure 9-5 Optional Components
Combining Protecting CHG and LD and Protecting CHG FET Protections