The MCU or bottom BQ769x2 DDSG turns on Q47 when the system needs the DSG MOSFET off which drives the Dri_Test node low. P-channel MOSFET Q49 is turned on to discharge gate-source voltage of the DSG MOSFET with R175. Zener D30 protects the Q49 source-gate voltage. The top BQ769x2 device drives TOP_DSG towards TOP_LD to turn off Q41, blocking further discharging of the charge pump and allowing Dri_Test to reach ground to make sure the DSG MOSFET turns off completely. D21 and R148 protect the Q41 gate-source voltage and make sure that Q41 is in the off state. When the DSG MOSFET is completely off, the PACK+ voltage is low, D24 blocks current from UP_GND and TOP_LD to charge PACK+ and protects the top BQ769x2 from negative voltage. Q47 is able to be turned off to save power after the DSG MOSFET turn off process finishes.

When the system needs to turn the DSG MOSFET on again, the system first checks that Q47 is off and then drives TOP_DSG with the top BQ769x2 charge pump voltage. Q41 is on and charges gate-source voltage of the DSG MOSFET through R147, Q41, R157, D29, and D30. Since D24 blocks TOP_LD from following PACK+ when PACK+ is low, TOP_LD can be charged too fast to slow down the turn on process of Q41. This design reserves R163 in parallel with D24 on the board but leaves R163 unconnected for lower current consumption. Schottky D23 is reserved to prevent negative voltage on TOP_LD for protection.