JAJSP77A November 2019 – August 2020 BQ79600-Q1
PRODUCTION DATA
INH pin is used if Reverse Wakeup feature is used. If this feature is not used, connect this pin to BAT pin, refer to schematic in Figure 8-1.
Reverse wakeup feature is a mechanism where BQ79600-Q1 can wakeup the host, through INH pin, on faulty status from either BQ79600-Q1 or stack devices like BQ7961X-Q1. MCU and its supply (PMIC/SBC) are in SHUTDOWN for power saving on low voltage battery side.
The INH pin is a high voltage output pin that provides voltage from the BAT minus VDROP_INH to enable an external high voltage regulators (SBC, PMIC). These regulators are usually used to support the microprocessor and VIO pin. When INH PMOS pullup is not activated, INH pin goes to a high Z state, it relies on external circuit to define the pin voltage (in application circuit, 100kohm resistor to GND is used.)
INH PMOS pullup can be triggered:
Once INH triggered, it remains latched in all modes as long as VBAT is not removed.
INH function described above can be disabled by configuring INH_DIS[1:0] = 2’b11.
Every time INH PMOS is activated, fault bit [INH] is set. To clear the fault, set INH_DIS[1:0] = 2’b11 (disarm INH driver), then write [RST_SYS] = 1. After this, to use INH feature, set INH_DIS[1:0] = 2’b00.
As part of safety diagnostic (SM202 in Safety Manual), host can trigger INH in ACTIVE and check if pin voltage is set properly: If INH pin voltage is higher than VINH_DET, [INH_STAT] = 1.
INH pin should be considered a "high voltage logic" terminal, thus should be used to drive the EN terminal of the system’s power management device. It should be not used as a switch for power management supply itself. This terminal is not reverse battery protected and thus should not be connected outside of the system module.