TLE 4275 V33

Block Description and Electrical Characteristics

Datasheet

7

Rev. 1.0, 2006-09-22

3.3

Reset Function

The reset function contains serveal features:

Output Undervoltage Reset:

An output undervoltage condition is indicated setting the Reset Output “RO” to low. This signal might be used to

reset a microcontroller during low supply voltage.

In case the battery voltage is already lower than the buffered output voltage

V

circuit is supplied from the output “Q”, ensuring a defined reset switching threshold also at

V

Output “RO” is held “low” down to an output voltage of

V

Power-On Reset Delay Time:

The power-on reset delay time

t

time period from exceeding the reset switching threshold

V

output “RO” from “low” to “high”. The power-on reset delay time

t

capacitor

C

V

For easy calculating the power-on reset delay time, a multiplier factor

F

Hence,

t

t

(1)

For a precise calculation consider also the delay capacitor’s tolerance.

Undervoltage Reset Delay Time:

Unlike the power-on reset delay time, the undervoltage reset delay

t

event where the delay capacitor

C

restarts. Therefore, the undervoltage reset delay time

t

starting from

V

For easy calculating the undervoltage reset delay time, a multiplier factor

F

becomes:

t

(2)

For a precise calculation consider also the delay capacitor’s tolerance.

Reset Reaction Time:

The total reset reaction rime

t

the external delay capacitor

C

becomes:

t

rr,total

=

t

(3)

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.