The nRST pin is a bi-directional open-drain low side driver that serves three functions, a V_CC monitor output for under-voltage events, restart mode indicator and a device input reset. The pin is nRST in Pin Control Mode and the defaulted function for SPI mode. This pin is internally pulled up to V_INT by a 45 kΩ resistor. V_INT represents the TLIN1431-Q1 IO voltage level and may or may not be V_CC. It is recommended to use an external 10 kΩ pull-up to the processor IO voltage rail. The pin can determine when an input pulse of t_nRSTIN is applied causing the device to enter restart mode. When an under-voltage event takes place, the nRST is latched low after a 30 µs filter and the device transitions to restart mode, fail-safe mode disabled, or fail-safe mode after the t_UVFLTR has expired. When in restart and V_CC exceeds the UV_CCR threshold, the t_{RSTN_act} timer starts. After this timer times out, the device transitions to standby mode, and the nRST pin is released. If a thermal shutdown event takes place, the signal is pulled to ground. When the device is configured by SPI, the pin can be programmed to become the watchdog output trigger to reset the processor. When the watchdog times out, this signal is pulled low for time of t_{NRST_TOG} and then released back to V_CC. If both are needed for SPI configuration it is recommended to add an external circuit off the LIMP pin to serve as the watchdog output trigger to reset the processor. Note the LIMP pin output is a high voltage output based upon V_SUP and care must be taken when connecting to a lower voltage device.