ZHCSRF8 December 2022 TPS3435
PRODUCTION DATA
The TPS3435 supports watchdog startup delay feature. This feature is activated after power up or after WDO assert event. When tSD frame is active, the device monitors the WDI pin but the WDO output is not asserted. This feature allows time for the host complete boot process before watchdog monitoring can take over. The start up delay helps avoid unexpected WDO assert events during boot. The tSD time is predetermined based on the device part number selected. Refer Section 5 section for details to map the part number to tSD time. Pinout option A, B, K are available only in no delay or 10 sec start up delay options.
The tSD frame is complete when the time duration selected for tSD is over or host provides a valid transition on the WDI pin. The host must provide a valid transition on the WDI pin during tSD time. The device exits the tSD frame and enters watchdog monitoring phase after valid WDI transition. Failure to provide valid transition on WDI pin triggers the watchdog error by asserting the WDO output pin.
The tSD frame is not initiated when the watchdog functionality is enabled using WD-EN pin or SET[1:0] pin or WDI float functionality as described in Section 8.3.1.2 section.
Figure 8-8 diagram shows the operation for tSD time frame.