l4937npd STMicroelectronics, l4937npd Datasheet - Page 5

• Manufacturer Part Number: l4937npd
• Description: Dual 5v Multifunction Voltage Regulator
• Manufacturer: STMicroelectronics

ELECTRICAL CHARACTERISTICS (continued)
RESET
Note : 1: Foldback characteristic
FUNCTIONAL DESCRIPTION
The L4937NDis based on the SGS-THOMSON Mi-
croelectronics modular voltage regulator approach.
Several out-standing features and auxiliary func-
tions are provided to meet the requirements of sup-
plying the microprocessor systems used in automo-
tive applications.
Furthermore the device is suitable also in other ap-
plications requiring two stabilized voltages.
The modular approach allows other features and
functions to be realized easily when required.
STANDBY REGULATOR
The standby regulator uses an Isolated Collector
Vertical PNP transistor as the regulating element.
This structure allows a very low dropout voltage at
currents up to 50mA. The dropout operation of the
standby regulator is maintained down to 2V input
supply voltage. The output voltage is regulated up
to the transientinput supplyvoltageof 40V.This fea-
ture avoids functional interruptions which could be
generated by overvoltage pulses.
Figure 1 : Output Voltage vs. Input Voltage.
Symbol
V
CTh, hyst
I
V
V
V
LRES
V
t
t
RD
RR
CTh
Rth
RL
Rt
Reset Low Threshold Voltage
Reset Threshold Hysteresis
Reset Pulse Delay
Reset Reaction Time
Reset Output LOW Voltage
Reset Output HIGH Leakage
Delay Comparator Threshold
Delay Comparator Threshold
Hysteresis
Parameter
C
C
R
V
V
S
RES
T
T
RES
= 100nF; t
= 100nF
= 1.5V
= 5V
= 10K to V
Test Conditions
R
The typical curve of the standby output voltage as a
functionof the input supply voltage is shown in fig. 1.
The current consumption of the device (quiescent
current) is less than 260 A when output 2 is dis-
abled (standby mode). The dropout voltage is con-
trolled to reduce the quiescent current peak in the
undervoltage region and to improve the transient
response in this region.
The quiescentcurrent isshown in fig. 2 as a function
of the supply input voltage 2.
OUTPUT 2 VOLTAGE
The output 2 regulator uses the same output struc-
ture as the standbyregulator, but rated for an output
current of 500mA.
The output 2 regulatorworks in tracking mode with
the standby output voltage as a reference voltage
when the output 2.
The output 2 regulator can be switched off via the
Enable input.
> 100 s
01
V
o1
Min.
50
55
1
-0.4
Typ.
100
100
100
4.7
2.0
10
V
Max.
o1
200
180
0.4
50
1
L4937NPD
-0.1
Unit
mV
mV
ms
V
V
V
A
s
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