TLE4678

Reset Function

Datasheet

18

Rev. 1.1, 2009-08-27

Reset Reaction Time

In case the output voltage of the regulator drops below the output undervoltage lower reset threshold

V

delay capacitor

C

threshold

V

Additionally to the delay capacitor discharge time

t

reaction rime

t

t

(3)

with

•

t

•

t

•

t

typical performance graphs.

Reset Ouput “RO”

The reset output “RO” is an open collector output with an integrated pull-up resistor. In case a lower-ohmic “RO”

signal is desired, an external pull-up resistor to the output “Q” can be connected. Since the maximum “RO” sink

current is limited, the optional external resistor

R

Reset Output “RO” Low for

V

In case of an undervoltage reset condition reset output “RO” is held “low” for

V

is 0 V. This is achieved by supplying the reset circuit from the output capacitor.

Reset Adjust Function

The undervoltage reset switching threshold can be adjusted according to the application’s needs by connecting

an external voltage divider (

R

GND. The reset adjustment range is given in Item 7.2.6.

When dimensioning the voltage divider, take into consideration that there will be an additional current constantly

flowing through the resistors.

With a voltage divider connected, the reset switching threshold

V

V

(4)

with

•

V

•

R

•

V