Window Frame to Reset the WDI

Detection of

Rising Edge

WDI

t

TPS3813J25-Q1, TPS3813L30-Q1

TPS3813K33-Q1, TPS3813I50-Q1

SPRS288B – MAY 2008 – REVISED APRIL 2012

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DETAILED DESCRIPTION

Implemented Window-Watchdog Settings

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

GND. There are four different timings available with these settings, as shown in the following table.

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 is shown in Figure 3. It is used to describe the

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 125°C.

In the shaded area of Figure 3, it cannot be predicted if the device will detect a violation or not and release a

Figure 3. Upper and Lower Boundary Visualization

Timing Rules of Window-Watchdog

After the reset of the supervisor is released, the lower boundary of the first WDI window is disabled. However,

after the first WDI pulse low-to-high transition is detected, the lower boundary function of the window is enabled.

All further WDI pulses need to fit into the configured window frame.

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