TLE42754

Block Description and Electrical Characteristics

Data Sheet

16

Rev. 1.1, 2008-09-24

5.3

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

t

from exceeding the reset switching threshold

V

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

t

charged by the delay capacitor charge current

I

If the application needs a power-on reset delay time

t

capacitor’s value can be derived from the specified values in Item 5.3.6 and the desired power-on delay time:

with

•

•

•

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

with

•

•

•

t

Reset Output Pull-Up Resistor

R

The Reset Output RO is an open collector output requiring an external pull-up resistor to a voltage

V

Table “Electrical Characteristics Reset Function” on Page 19 a minimum value for the external resistor

R

RO

is given for the case it is connected to

V

voltage

V

,

---------------- 47nF

×

=

,

,

+

=

5k

Ω

----------- V

IO

×

=