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TPS3813J25, TPS3813L30, TPS3813K33, TPS3813I50

SLVS331H – DECEMBER 2000 – REVISED JULY 2016

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Product Folder Links: TPS3813J25 TPS3813L30 TPS3813K33 TPS3813I50

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Copyright © 2000–2016, Texas Instruments Incorporated

Feature Description (continued)

8.3.1 User-Programmable Watchdog Timer (WDI)

The TPS3813xxx family of devices have a watchdog timer that must be periodically triggered by either a positive

or negative transition at the WDI pin to avoid a reset signal being issued. When the supervising system fails to

This event also reinitializes the watchdog timer. After the reset of the supervisor is released, the lower boundary

of the first WDI window is disabled. After the first WDI low-to-high transition is detected, the lower boundary

function of the window is enabled. All further WDI pulses must fit into the configured window frame.

Both the upper and lower boundary of the window can be adjusted by the user. See Programming for more

details on how to set the upper and lower boundaries of the window.

8.3.2 RESET Output

then RESET is asserted, driving the RESET pin to a low impedance.

state and uses a pullup resistor to hold RESET high. Connect the pullup resistor to the proper voltage rail to

enable the outputs to be connected to other devices at the correct interface voltage level. RESET can be pulled

up to any voltage up to 6 V, independent of the device supply voltage. To ensure proper voltage levels, give

some consideration when choosing the pullup resistor value and consider the required low-level output voltage

8.4 Device Functional Modes

Table 1 summarizes the various functional modes of the device.

Table 1. TPS3813xxx Function/Truth Table

WDI

RESET

—

Undefined

—

L

Outside window

L

Inside window

H

•

WDI pulse inside window: as long as pulses occur within the user-programmable window, the RESET signal

remains high.

•

WDI pulse outside window: if a pulse occurs outside the user-programmable window or not at all, the RESET

signal goes low.

RESET signal is asserted regardless of the WDI signal.

asserted output low, and RESET is undefined and must not be relied upon for proper device function.