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DETAILED DESCRIPTION

IMPLEMENTED WINDOW-WATCHDOG SETTINGS

Window Frame to Reset the WDI

Detection of

Rising Edge

WDI

t

TPS3813J25, TPS3813L30

TPS3813K33, TPS3813I50

SLVS331B – DECEMBER 2000 – REVISED JUNE 2005

Terminal Functions

TERMINAL

I/O

DESCRIPTION

NAME

NO.

GND

2

I

Ground

RESET

6

O

Open-drain reset output

4

I

Supply voltage and supervising input

WDI

1

I

Watchdog timer input

WDR

5

I

Selectable watchdog window ratio input

WDT

3

I

Programmable watchdog delay input

There are two different ways to set up the watchdog window. The first way is to use the implemented timing

GND. There is a total of four different timings available with these settings. They are listed in the table below.

SELECTED OPERATION MODE

WINDOW FRAME

LOWER WINDOW FRAME

Max = 0.3 s

Max = 9.46 ms

WDR = 0 V

Typ = 0.25 s

Typ = 7.86 ms

Min = 0.2 s

Min = 6.27 ms

WDT = 0 V

Max = 0.3 s

Max = 2.43 ms

Typ = 0.25 s

Typ = 2 ms

Min = 0.2 s

Min = 1.58 ms

Max = 3 s

Max = 93.8 ms

WDR = 0 V

Typ = 2.5 s

Typ = 78.2 ms

Min = 2 s

Min = 62.5 ms

Max = 3 s

Max = 23.5 ms

Typ = 2.5 s

Typ = 19.6 ms

Min = 2 s

Min = 15.6 ms

To visualize the values named in the table, a timing diagram was prepared. It is used to describe the upper and

these values, the watchdog timer should be retriggered to avoid a timeout condition or a boundary violation in the

event of a trigger pulse in the lower boundary. The values in the table above are typical and worst case

conditions. They are valid over the whole temperature range of –40

°C to 85°C.

In the shaded area of Figure 1, it cannot be predicted if the device will detect a violation or not and release a

Figure 1. Upper and Lower Boundary Visualization

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