SLUUDA0A April 2026 – July 2026 BQ27Z855
The system can signal the gas gauge via the PRES function to open the CFET and DFET, disconnecting the battery power to the host. The device operates in embedded pack configuration ([NR] = 1).
Feature prerequisites: The System Disconnect feature is active only when all of the following conditions are met:
The internal pullup of the PRES function is enabled for this feature when assigned to a GPIO pin. Entry to the SYSTEM DISCONNECT mode occurs when the gas gauge detects a high-to-low transition of the configured PRES pin (PRES pin debounce is used). The gauge opens the CFET and DFET in SYSTEM DISCONNECT mode. The OperationStatus()[DISCONN] = 1.
Because the system is shutdown in this mode, the gas gauge enters SLEEP mode after a bus timeout. Regardless if the [SLEEPCHG] flag sets, the CFET and DFET will remain off in the SYSTEM DISCONNECT mode.
The PRES pin state is sampled in 250-ms intervals. A "low" is detected by receiving SYS_PRES Delay consecutive low samples. The debounce time ranges from SYS_PRES Delay − 1 samples (if the pin state is changed just before a sample is taken) to SYS_PRES Delay samples (if the pin state is changed just after a sample is taken).
It exits from the SYSTEM DISCONNECT mode when:
The gauge then returns to NORMAL mode and closes the CFET and DFET.
Pin Configuration: The PRES function can be assigned to pin C1 (if it is not configured as a TS pin), C2, or C3. Configure via the IO Config data flash settings.