L4949EP datasheet(4/10 Pages) STMICROELECTRONICS

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APPLICATION INFORMATION

Supply Voltage Transient

High supply voltage transients can cause a reset

output signal disturbation.

For supply voltages greater than 8V the circuit

shows a high immunity of the reset output against

supply transients of more than 100V/

µs.

For supply voltages less than 8V supply tran-

sients of more than 0.4V/

µs can cause a reset

signal disturbation.

To improve the transient behaviour for supply

voltages less than 8V a capacitor at pin 3 can be

used.

A capacitor at pin 3 (C3

≤ 1µF) reduces also the

output noise.

FUNCTIONAL DESCRIPTION

The L4949E is a monolithic integrated voltage

regulator, based on the STM modular voltage

regulator approch. Several outstanding features

and auxiliary functions are implemented to meet

the requirements of supplying microprocessor

systems in automotive applications. Nevertheless,

it is suitable also in other applications where the

present functions are required. The modular ap-

proach of this device allows to get easily also

other features and functions when required.

Voltage Regulator

The voltage regulator uses an Isolated Collector

Vertical PNP transistor as a regulating element.

Figure 1: Foldback Characteristic of VO

REG

1.23V

REF

RES

GND

D96AT219

PREREGULATOR 5V

RESET

SENSE

1.23V

OUT

Z (optional)

BAT

OUT

APPLICATION CIRCUIT

For stability: CS

≥ 1µF, CO ≥ 4.7µF, ESR < 10Ω at 10KHz

Recommended for application: CS =CO =10

µF to 100µF

L4949E

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