TLE4291E View Datasheet(PDF) - Infineon Technologies

Part Name

Description

Manufacturer

TLE4291E

Low Drop Out Linear Voltage Regulator

Infineon Technologies 

TLE4291

Reset Function

8

Reset Function

8.1

Description 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 td,PWR-ON allows a microcontroller and oscillator to start up. This delay time is the

time period from exceeding the reset switching threshold until the reset is released by switching the reset output

“RO” from “low” to “high”. The power-on reset delay time td,PWR-ON is defined by an external delay capacitor CD

connected to pin “D” which is charged up by the delay capacitor charge current ID,ch starting from VD = 0 V.

In case a power-on reset delay time td,PWR-ON different from the value for CD = 100nF is required, the delay

capacitor’s value can be derived from the specified value given in Item 8.2.13:

CD = 100nF × td,PWR-ON / td,PWR-ON,100nF

(1)

with

• td,PWR-ON: Desired power-on reset delay time

• td,PWR-ON,100nF: Power-on reset delay time specified in Item 8.2.13

• CD: Delay capacitor required.

The formula is valid for CD ≥ 10nF. For precise timing calculations consider also the delay capacitor’s tolerance.

Reset Reaction Time

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

delay capacitor CD is discharged rapidly. Once the delay capacitor’s voltage has reached the lower delay switching

threshold VDST,lo, the reset output “RO” will be set to “low”.

Additionally to the delay capacitor discharge time trr,d, an internal reaction time trr,int applies. Hence, the total reset

reaction rime trr,total becomes:

trr,total = trr,int + trr,d

(2)

with

• trr,total: Total reset reaction time

• trr,int: Internal reset reaction time; see Item 8.2.14.

• trr,d: Delay capacitor discharge time. For a capacitor CD different from the value specified in Item 8.2.15, see

typical performance graphs.

Reset Output “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 RRO,ext must not below as specified in Item 8.2.7.

Data Sheet

17

Rev. 1.1, 2012-12-03

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