SLUUCH2 User guide

SLUUCH2 March 2021 BQ40Z50-R2

5.4.1 VOLTAGE BASED SHUTDOWN

To minimize power consumption and to avoid draining the battery, the device can be configured to shut down at a programmable stack voltage threshold. This function also works in PERMANENT FAILURE mode. When the device is in PERMANENT FAILURE mode, the parameters PF Shutdown Voltage and PF Shutdown Time configure the shutdown threshold.

Status	Condition	Action
Enable	Min cell voltage < *Shutdown Voltage*	OperationStatus()[SDV] = 1
Trip	Min cell voltage < *Shutdown Voltage* for *Shutdown Time*	Turn DSG FET off
Shutdown	Voltage at PACK pin < *Charger Present Threshold*	Send device into SHUTDOWN mode
Exit	Voltage at PACK pin > V_STARTUP	OperationStatus()[SDV] = 0 Return to NORMAL mode

Table 5-1 PF Shutdown Voltage

Class	Subclass	Name	Format	Size in Bytes	Min Value	Max Value	Default Value	Unit
Power	Shutdown	PF Shutdown Voltage	Int	2	0	32767	1750	mV

Table 5-2 PF Shutdown Time

Class	Subclass	Name	Format	Size in Bytes	Min Value	Max Value	Default Value	Unit
Power	Shutdown	PF Shutdown Time	Unsigned Int	1	0	255	10	s

Note:

The BQ40Z50-R4 device goes through a full reset when exiting from SHUTDOWN mode, which means the device will reinitialize. On power up, the gauge will check some special memory locations. If the memory checksum is incorrect, or if the gauge or the AFE watchdog has been triggered, the gauge will do a full reset.

If the memory checksum is good, for example, in a case of a short power glitch, the gauge will do a partial reset. The initialization is faster in a partial reset, and certain memory data will not be reinitialized (for example, all SBS registers, last known FET state, last ADC and CC readings, and so on), and so a partial reset is usually transparent to the host.