TLE42994

Block Description and Electrical Characteristics

Data Sheet

21

Rev. 1.2, 2014-07-03

5.6

Reset Function

The reset function provides several features:

Output Undervoltage Reset:

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

to reset a microcontroller during low supply voltage.

Power-On Reset Delay Time:

The power-on reset delay time

frame from exceeding the reset switching threshold

V

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

t

to pin D charged by the delay capacitor charge current

I

If the application needs a power-on reset delay time

Time, the delay capacitor’s value can be derived from the specified values in Power On Reset Delay Time and

the desired power-on delay time:

(1)

with

•

C

•

t

•

t

For a precise calculation also take the delay capacitor’s tolerance into consideration.

Reset Reaction Time:

The reset reaction time avoids that short undervoltage spikes trigger an unwanted reset “low” signal. The reset

reaction rime

t

capacitor

C

(2)

with

•

t

•

t

•

t

Optional Reset Output Pull-Up Resistor

R

The Reset Output RO is an open collector output with an integrated pull-up resistor. If needed, an external pull-up

resistor to the output Q can be added. In Table 7 “Electrical Characteristics Reset Function” on Page 24 a

minimum value for the external resistor

R

,

---------------- 100nF

×

=

,

,

+

=