8 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

8.1 Application Information

8.1.1 Lower-Boundary Calculation

The lower boundary can be calculated based on the values listed in the Section 6.7 table. Additionally, facts

must be taken into account to verify that the lower boundary is where it is expected. Because the internal

oscillator of the window watchdog is running free, any rising edge at the WDI pin is taken into account at the

next internal clock cycle. Accounting for any rising edge at the WDI pin occurs regardless of the external source.

Because the shift between internal and external clock is not known, consider the worst-case condition when

calculating this value.

Table 8-1. Watchdog Lower-Boundary Calculation

SELECTED OPERATION MODE

LOWER BOUNDARY OF FRAME

WDT = external capacitor C(ext)

WDR = 0 V

tboundary,max = twindow,max / 23.5

tboundary,typ = twindow,typ / 25.8

tboundary,min = twindow,min / 28.7

WDR = VDD

tboundary,max = twindow,max / 51.6

tboundary,typ = twindow,typ / 64.5

tboundary,min = twindow,min / 92.7

8.2 Typical Application

A typical application example (see Figure 8-1) is used to describe the function of the watchdog in more detail.

WDI

WDR

WDT

GND

TPS3813-Q1

I/O

GND

Position 1

Position 2

Position 3

Position 5

Position 4

R

18 kΩ

µC

C

(ext)

V

DD

V

DD

V

DD

0.1 µF

0.1 µF

V

DD

V

DD

RESET

RESET

Figure 8-1. Application Example

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TPS3813K33-Q1, TPS3813I50-Q1

SPRS288H – MAY 2008 – REVISED OCTOBER 2021

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