VDD

WDI

Ignore

ttSDt

ttWDOt

VPOR

ttWDt

ttWDt

ttSDt

Ignore

tSTRT

WDO

VDDMIN

Figure 8-8. tSD Frame Behavior

8.3.1.4 SET Pin Behavior

The TPS3435 offers one or two SET pins based on the pinout option selected. SET pins offer flexibility to the

user to program the tWD timer on the fly to meet various application requirements. Typical use cases where SET

pin can be used are:

• Use wide timeout timer when host is in sleep mode, change to small timeout operation when host is

operational. Watchdog can be used to wake up the host after long duration to perform the application related

activities before going back to sleep.

• Change to wide timeout timer when performing system critical tasks to make sure the watchdog does not

interrupt the critical task. Change timer to application specified interval after the critical task is complete.

The tWD timer value for the device is combination of timer selection based on the CWD pin or fixed timer value

along with SET pin logic level. The base tWD timer value is decided based on the Watchdog Time selector in

the Section 5 section. The SET pin logic level is decoded during the device power up. The SET pin value can

be changed any time during the operation. SETx pin change which leads to change of watchdog timer value

or enable disable state, terminates the ongoing watchdog frame immediately. SETx pins can be updated when

WDO output is asserted as well. The updated tWD timer value will be applied after output is deasserted and the

tSD timer is over or terminated.

For a pinout which offers only SET0 pin to the user, the tWD multiplier value is decided based on the Watchdog

Time Scaling selector in the Section 5 section. Table 8-1 showcases an example of the tWD values for different

SET0 logic levels when using Watchdog Time setting as option D = 10 msec.

Table 8-1. tWD Scaling with SET0 Pin Only

WATCHDOG TIME SCALING SELECTION

tWD

SET0 = 0

SET0 = 1

A

10 msec

20 msec

B

10 msec

40 msec

C

10 msec

80 msec

D

10 msec

160 msec

E

10 msec

320 msec

F

10 msec

640 msec

G

10 msec

1280 msec

For pinouts which offer both SET0 & SET1 pins to the user, the tWD multiplier value is decided based on the

Watchdog Time Scaling selector in the Section 5 section. Two SETx pins offer 3 different time scaling options.

The SET[1:0] = 0b'01 combination disables the watchdog operation. Table 8-2 showcases an example of the

TPS3435

SNVSCF7 – DECEMBER 2022

www.ti.com

18

Submit Document Feedback

Copyright © 2022 Texas Instruments Incorporated

Product Folder Links: TPS3435