L4937NPD Просмотр технического описания (PDF) - STMicroelectronics
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L4937NPD Datasheet PDF : 9 Pages
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L4937NPD
ELECTRICAL CHARACTERISTICS (continued)
RESET
Symbol
VRt
VRth
tRD
tRR
VRL
Parameter
Reset Low Threshold Voltage
Reset Threshold Hysteresis
Reset Pulse Delay
Reset Reaction Time
Reset Output LOW Voltage
ILRES
VCTh
VCTh, hyst
Reset Output HIGH Leakage
Delay Comparator Threshold
Delay Comparator Threshold
Hysteresis
Note : 1: Foldback characteristic
Test Conditions
CT = 100nF; tR > 100µs
CT = 100nF
RRES = 10KΩ to V01
VS = 1.5V
VRES = 5V
Min.
Vo1 -0.4
50
55
1
Typ.
4.7
100
100
10
Max.
Vo1 -0.1
200
180
50
0.4
Unit
V
mV
ms
µs
V
1
µA
2.0
V
100
mV
FUNCTIONAL DESCRIPTION
The L4937ND is 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 transient input supply voltage of 40V. This fea-
ture avoids functional interruptions which could be
generated by overvoltage pulses.
Figure 1 : Output Voltage vs. Input Voltage.
The typical curve of the standby output voltage as a
function of the input supply voltage is shown in fig. 1.
The current consumption of the device (quiescent
current) is less than 260µA 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 quiescent current is shown 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 standby regulator, but rated for an output
current of 500mA.
The output 2 regulator works 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.
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