TPS65381A-Q1: Distinguish between Power On Reset and CPU Reset

Hi Shinichi-san,

There is not a direct way in the TPS65381A-Q1 to determine if the PMIC went through a power on reset on the PMIC side (NPOR) or the PMIC transitioned through the RESET state. Both will pull the NRES pin of the PMIC low and cause reset to the MCU. However, the MCU can determine this indirectly.

The indirect way to determine if the PMIC went through NPOR or just RESET state transition is to read one or more of the configuration registers that are only re-initialized by NPOR of the PMIC and configured by the application with values that are not default from the PMIC. A couple examples of such registers are the SAFETY_FUNC_CFG Register, SAFETY_CFG_CRC Register, SAFETY_PWD_THR_CFG Register, SAFETY_ERR_PWM_H Register, SAFETY_ERR_PWM_L Register, etc. So if the PMIC is reset from a NPOR these registers will be re-initialized to their default values, but if the PMIC just transitions through RESET state the values configured by the MCU in the application will remain in the registers after the RESET state. The MCU can read these registers when it boots to tell if a NPOR or RESET state only transition happened on the PMIC.

Please let us know if you have further questions.