9.2.1 Supply Rail Monitoring with Watchdog Time-out and 200-ms Delay

The TPS3823-xx-Q1 can be used to monitor the supply rail for devices such as microcontrollers. The downstream device is enabled by the TPS3823-xx-Q1 once the voltage on the supply pin (V_DD) is above the internal threshold voltage (V_IT– + V_HYS). The downstream device is disabled by the TPS3823-xx-Q1 when V_DD falls below the threshold voltage minus the hysteresis voltage (V_IT–). The TPS3823-xx-Q1 also issues a reset signal if the WDI input is not periodically triggered by a positive or negative transition at WDI. When the supervising system fails to retrigger the watchdog circuit within the time-out interval, t_tout, RESET becomes active for the time period t_d.

Some applications require a shorter reset signal than the 200 ms that most of the TPS382x-xx-Q1 family provide. In these cases, the TPS3820-xx-Q1is a good choice because it has a delay time of only 25 ms. If an open-drain output is needed, replace the TPS3823-xx-Q1 with the TPS3828-xx-Q1 (if the WDI input must be active while RESET is low, see Decoupling WDI During Reset Event). Figure 9 shows the TPS3823-33-Q1 in a typical application.

Figure 9. Supply Rail Monitoring With Watchdog Time-out