L4949E
APPLICATION CIRCUIT
V
OUT
V
Z (optional)
V
BAT
V
S
CT
PREREGULATOR 5V
2µ
+
RES
2V
REG
RESET
V
S
SI
V
OUT
SO
1.23V
REF
SENSE
1.23V
GND
D96AT219
For stability: C
S
≥
1µF, C
O
≥
4.7µF, ESR < 10Ω at 10KHz
Recommended for application: C
S
= C
O
= 10µF to 100µF
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-
4/10
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 V
O
STMICROELECTRONICS [ STMICROELECTRONICS ]
