The TPS3813xxx family of devices have a watchdog timer that must be periodically triggered by either a positive or negative transition at the WDI pin to avoid a reset signal being issued. When the supervising system fails to retrigger the watchdog circuit within the time-out interval, t_t(out), RESET becomes asserts for the time period t_d. This event also reinitializes the watchdog timer. After the reset of the supervisor is released, the lower boundary of the first WDI window is disabled. After the first WDI low-to-high transition is detected, the lower boundary function of the window is enabled. All further WDI pulses must fit into the configured window frame.

Both the upper and lower boundary of the window can be adjusted by the user. See Section 7.5 for more details on how to set the upper and lower boundaries of the window.