SLUUCY8 December 2023 BQ77307
The BQ77307 device includes an evaluation of the VSS voltage during each CHECK interval, comparing the resulting value to a threshold, to implement the VSS Diagnostic Protection. If the internal detection mux were to malfunction and remain fixed on one particular input, whether that being a cell voltage input, a thermistor, or a diagnostic check, this check of VSS helps make sure this condition is detected. When detected, the device triggers the VSS Diagnostic Protection Fault and sets 0x03 Safety Status B()[VSS], if enabled, and the device can disable FETs based on Settings:Protection:Both FET Protections B[VSS]. The fault can be recovered by the host sending the 0x009B PROT_RECOVERY()[DIAGREC] subcommand. The diagnostic protection alert is triggered whenever the VSS voltage is detected above approximately 100 mV. The diagnostic protection status fault is triggered when this occurs for two consecutive CHECK intervals.