The BQ41Z50 device can permanently disable the use of the battery pack in case of a significant failure. The permanent failure checks, except for IFC and DFW, can be enabled or disabled individually by setting the appropriate bit in Settings:Enabled PF A, Settings:Enabled PF B, Settings:Enabled PF C, and Settings:Enabled PF D. All permanent failure checks, except for IFC and DFW, are disabled until ManufacturingStatus()[PF] is set. When any PFStatus() bit is set, the device enters PERMANENT FAIL mode and the following actions are taken in sequence:
- Precharge, charge, and discharge FETs are turned off.
- OperationStatus()[PF] = 1, [XCHG] = 1, [XDSG] = 1
- The following SBS data is changed: BatteryStatus()[TCA] = 1, BatteryStatus()[TDA] = 1, ChargingCurrent() = 0, and ChargingVoltage() = 0.
- A backup of the internal AFE hardware registers are written to data flash: AFE Interrupt Status, AFE FET Status, AFE RXIN, AFE Latch Status, AFE Interrupt Enable, AFE FET Control, AFE RXIEN, AFE RLOUT, AFE RHOUT, AFE RHINT, AFE Cell Balance, AFE AD/CC Control, AFE ADC Mux, AFE LED Output, AFE State Control, AFE LED/Wake Control, AFE Protection Control, AFE OCD, AFE SCC, AFE SCD1, and AFE SCD2.
- The black box data of the last three SafetyStatus() changes leading up to PF with the time difference is written into the black box data flash along with the 1stPFStatus() value.
- The following SBS values are preserved in data flash for failure analysis:
- SafetyAlert()
- SafetyStatus()
- PFAlert()
- PFStatus()
- OperationStatus()
- ChargingStatus()
- GaugingStatus()
- Voltages in DAStatus1()
- Current()
- TSINT, TS1, TS2, TS3, and TS4 from DAStatus2()
- Cell DOD0 and passed charge
- Data flash writing is disabled (except to store subsequent PFStatus() flags).
- The FUSE pin is driven high if configured for specific failures and Voltage() is above Min Blow Fuse Voltage or there is a CHG FET (CFETF) or DSG FET (DFETF) failure. The FUSE pin will remain asserted until the Fuse Blow Timeout expires.
Note: If [PACK_FUSE] = 0, Voltage() is used to check for Min Blow Fuse Voltage, indicating the fuse is connected to the BAT side.
If [PACK_FUSE] = 1 (that is, the fuse is connected to the PACK side and is required to have a charger connected in order to blow the fuse), then the PACK voltage is used to check for Min Blow Fuse Voltage threshold.
While the device is in PERMANENT FAIL mode, any new SafetyAlert(), SafetyStatus(), PFAlert(), and PFStatus() flags that are set are added to the permanent fail log. Any new PFStatus() flags that occur during PERMANENT FAIL mode can trigger the FUSE pin. In addition, new PFStatus() flags are recorded in the Black Box Recorder 2nd and 3rd PF Status entries.