WDI

WDR

WDT

GND

TPS3813

I/O

GND

Position1

Position2

Position3

Position5

Position4

R

mC

C

(ext)

V

DD

V

DD

V

DD

0.1 F

m

0.1 F

m

V

DD

V

DD

RESET

RESET

TPS3813J25-Q1, TPS3813L30-Q1

TPS3813K33-Q1, TPS3813I50-Q1

SPRS288B – MAY 2008 – REVISED APRIL 2012

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Application Example

A typical application example (see Figure 4) is used to describe the function of the watchdog in more detail.

To configure the window watchdog function, two pins are provided by the TPS3813. These pins set the window

timeout and ratio.

The window watchdog ratio is a fixed ratio, which determines the lower boundary of the window frame. It can be

configured in two different frame sizes.

value based on a ratio calculation of the overall window timeout size: For the watchdog timeout pin (WDT)

capacitor connected to WDT, it is a ratio of 1:64.5.

If the window watchdog ratio pin (WDR) is set to GND, Position 2, the lower window frame will be a value based

on a ratio calculation of the overall window timeout size: For the watchdog timeout pin (WDT) connected to GND,

WDT it will be 1:25.8.

The watchdog timeout can be set in two fixed timings of 0.25 second and 2.5 seconds for the window or can by

programmed by connecting a external capacitor with a low leakage current at WDT.

boundary is 19.6 ms.

Figure 4. Application Example

6

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