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L4938N View Datasheet(PDF) - STMicroelectronics

Part Name
Description
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L4938N
STMICROELECTRONICS
STMicroelectronics STMICROELECTRONICS
L4938N Datasheet PDF : 12 Pages
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L4938N - L4938ND - L4938NPD
ELECTRICAL CHARACTERISTICS (continued)
RESET
Symbol
Parameter
Test Conditions
Min. Typ. Max. Unit
VRt Reset Low Threshold Voltage
VRth Reset Threshold Hysteresis
tRD
Reset Pulse Delay
tRR
Reset Reaction Time
CT = 100nF; tR > 100µs
CT = 100nF
Vo1 -0.4 4.7 Vo1 -0.1 V
50
100 200 mV
55
100 180 mV
1
10
50
µs
VRL Reset Output LOW Voltage
RRES = 10Kto V01
0.4
V
VS = 1.5V
ILRES
) VCTh
ct(s VCTh, hyst
Reset Output HIGH Leakage
Delay Comparator Threshold
Delay Comparator Threshold
Hysteresis
du SENSE
VRES = 5V
1
µA
2.0
V
100
mV
Pro t(s) VSlth
VSlth, hyst
lete uc VSOL
Sense Threshold Voltage
Sense Threshold Hysteresis
Sense Output LOW Voltage
so rod ILSO Sense Output Leakage
VSI = 1,16V; VS 3V
RSO = 10Kto V01
VSO = 5V; VSI 1.5V
1.16 1.23 1.35
V
40
100 200 mV
0.4
V
1
µA
b P Note : 1 : VO2 connected to ADJ.VO2 can be set to higher values by inserting an external resistor divider.
- O te 2 : Foldback characteristic
t(s) sole FUNCTIONAL DESCRIPTION
c b The L4938N is based on the STMicroelectronics
u O modular voltage regulator approach. Several out-
d - standing features and auxiliary functions are pro-
ro ) vided to meet the requirements of supplying the mi-
P t(s croprocessor systems used in automotive applica-
te c tions.
le u Furthermore the device is suitable also in other ap-
d plications requiring two stabilized voltages.
so ro The modular approach allows other features and
b P functions to be realized easily when required.
O te STANDBY REGULATOR
ole The standby regulator uses an Isolated Collector
sVertical PNP transistor as the regulating element.
bThis structure allows a very low dropout voltage at
Ocurrents up to 50mA. The dropout operation of the
The current consumption of the device (quiescent
current) is less than 250µA 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 programming pin ADJ is con-
nected to VO2. By connecting a resistor divider R1,
standby regulator is maintained down to 2V input R2 to the pin ADJ as shown in fig. 3, the output volt-
supply voltage. The output voltage is regulated up age 2 can be programmed to the value :
to the transient input supply voltage of 40V. This fea-
ture avoids functional interruptions which could be
VO2 = VO1 (1 + R1/R2)
generated by overvoltage pulses.
The typical curve of the standby output voltage as a
function of the input supply voltage is shown in fig. 1.
The output 2 regulator can be switched off via the
Enable input.
If a fixed 5 regulation is required ADJ Pin has to be
connected to V02 Pin.
5/12
 

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