8.3.7 Thermal Shutdown and Warning

Thermal shutdown occurs when the Thermal Shutdown (TSD) sensor senses an over-temperature condition. The sensor operates without interaction and is separated from the ADC measured die sensor. The TSD function has a register-status indicator flag (SYS_FAULT1[TSD]) that is saved during the shutdown event and can be read after the WAKEUP procedure. When a TSD fault occurs, the part immediately enters the SHUTDOWN state. Any pending transactions on UART or daisy chain are discarded. There is no fault signaling done when a thermal shutdown event occurs, as the device immediately shuts down. The BQ79606A-Q1 does not exit SHUTDOWN automatically. To awaken the part, follow the normal WAKEUP procedure and make sure the ambient temperature is below thermal T_{SD_FALL}. Once the die temperature falls below T_{SD_FALL} and the WAKEUP command is received, the BQ79606A-Q1 follows the normal startup procedure. Upon waking up, the SYS_FAULT1[TSD] bit is set and, if unmasked, a FAULT Is indicated.

To warn the host of an impending thermal overload, the BQ79606A-Q1 includes an over-temperature warning that signals a fault when the die temperature approaches thermal shutdown. With every cell ADC conversion, the temperature read is compared against the thermal warning threshold (Twarn). A fault is signaled when the read die temperature is greater than the threshold. When an unmasked temperature warning fault occurs, the SYS_FAULT1[TWARN] bit is set. If unmasked, the NFAULT (base device) or FAULT* interface (stack device) signals the fault. The application must utilize the thermal warning and die temperature ADC measurements to avoid thermal shutdown events.