Datasheet L4937N Datasheet (SGS Thomson Microelectronics)



DUAL MULTIFUNCTIONVOLTAGE REGULATOR

.

STANDBYOUTPUTVOLTAGEPRECISION5V
± 2%

.

OUTPUT2TRACKEDTOTHESTANDBYOUT­PUT

.OUTPUT 2 DISABLE FUNCTION FOR

STANDBYMODE

.VERY LOW QUIESCENT CURRENT, LESS

THAN250µA,IN STANDBYMODE

.OUTPUTCURRENTS: I

.

VERYLOW DROPOUT(max 0.4V/0.6V)

=50mA,I02=500mA

01

.OPERATINGTRANSIENTSUPPLYVOLTAGE

UP TO 40V

.POWER-ON RESET CIRCUIT SENSING THE

STANDBYOUTPUTVOLTAGE

.POWER-ONRESET DELAYPULSEDEFINED

BY THEEXTERNALCAPACITOR

.

THERMALSHUTDOWNANDSHORTCIRCUIT
PROTECTIONS

L4937N

Heptawatt

ORDERING NUMBER : L4937N

DES CRIP T ION

TheL4937Nis amonolithicintegrateddual voltage
regulatorswithtwoverylowdropoutoutputsandad­ditionalfunctionssuch as power-onresetand input
voltage sense. It is designed for supplying micro­computer controlled systems specially in automo­tiveapplications.

PIN CONNECTI ON

(top view)

June 2000

1/9

L4937N

BLOCK DIAGRAM

THERMAL DATA

Symbol Parameter Value Unit

2/9

R

thj-case

Thermal Resistance Junction-Case Max. 3

C/W

°

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

DC Supply Voltage 28 V

S

Transient Supply Voltage (T < 1s) 40 V

T

j,Tstg

I

EN

V

EN

V

RES

I

RES

P

Note : The circuit is ESD protected according to MIL–STD–883C.

Junction and Storage Temperature Range –55 to 150
Enable Input Current (V

EN

0.3V)

≤

Enable Input Voltage V

1

±

S

Reset Output Voltage 20 V
Reset Output Current 5 mA
Power Dissipation (TA=80°C, R

D

th heatsink

=9°C/W)

5W

APP LICATIO N CIRCUIT

L4937N

C

°

mA

CS≥ 1µF;C01≥ 6µF;C02≥ 10µF, ESR < 10Ω at 10KHz

3/9

L4937N

ELECTRICAL CHARACTERISTICS (VS= 14V; –40°C ≤ Tj≤ 125°C unless otherwise specified)

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

V

V

O2-VO1

V

DP1

V

V

DP2

V

V

OL1.2

V

OLO1

V

OLO2

I

LIM1

I

LIM2

I

QSB

I

Operating Supply Voltage 25 V

S

Standby Output Voltage

O1

Output Voltage 2 Tracking Error
(note 1)

6V≤V
1mA≤I

6V≤V
5mA ≤ I

≤

S

≤

O1

≤

S

≤ 500mA

O2

25V

50mA

25V

4.90 5.00 5.10 V

–25 +25 mV

Enable = LOW

Dropout Voltage 1 IO1= 10mA

Input to Output Voltage

IO1

= 50mA

I

O1

VS = 4V, IO1= 35mA 0.4 V

0.1

0.2

Difference in Undervoltage
Condition

Dropout Voltage 2 IO2 = 100mA

Input to Output Voltage

IO2

= 500mA

I

O2

VS = 4.6V, IO2= 350mA 0.6 V

0.2

0.3

Difference in Undervoltage
Condition

Line Regulation

Load Regulation 1
Load Regulation 2

6V ≤ V

I

O1

1mA≤I
5mA≤I

Current Limit 1 VO1= 4.5V

V

O1

≤ 25V

S

= 1mA; IO2= 5mA

50mA

≤

O1

500mA

≤

O2

= 0V (note 2)

55
25

100

50
Current Limit 2 VO2 = 0V 550 1000 1700 mA
Quiescent Current Standby

Mode (output 2 disabled)

Quiescent Current IO1= 50mA

Q

= 0.3mA; TJ< 100°C

I

O1

2.4V

V

≥

EN

= 14V

V

S

= 3.5V

V

S

= 500mA

I

O1

210
340

0.25

0.4

0.3

0.6

20 mV

25 mV
50 mV

200
100

290
850

30 mA

V
V

V
V

mA
mA

µ
µ

A
A

ENABLE

V

ENL

V

ENH

V

ENhyst

I

EN

4/9

Enable Input LOW Voltage

–0.3 1.5 V

(output 2 active)
Enable Input HIGH Voltage 2.4 7 V
Enable Hysteresis 30 75 200 mV
Enable Input Current 0V < VEN< 1.2V

2.5V < V

EN

<7V

–10–1–1.50–0.5

+1

µ
µ

A
A

L4937N

ELECTRICAL CHARACTERISTICS

(continued)

RESET

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

V

t

RD

t

RR

V

I

LRES

V

CTth

V

CTth,hyst

Note :

FUNCTI ON AL DESCRIPTION

The L4937Nis based on the SGS-THOMSON Mi­croelectronicsmodularvoltageregulatorapproach.
Several out-standing features and auxiliary func­tionsareprovidedtomeet therequirementsof sup­plyingthemicroprocessorsystemsusedinautomo­tiveapplications.

Furthermorethedevice issuitablealso inother ap­plicationsrequiringtwo stabilizedvoltages.

The modular approach allows other features and
functionsto be realizedeasilywhen required.

STANDBYREGULATOR
The standby regulator uses an Isolated Collector

Vertical PNP transistor as the regulatingelement.
This structure allowsa verylow dropout voltageat
currentsup to 50mA. The dropout operationof the
standby regulator is maintained down to 2V input
supply voltage. The outputvoltage is regulatedup
tothetransientinputsupplyvoltageof40V.Thisfea­ture avoids functionalinterruptions which could be

Reset Low Threshold Voltage VS= 14V Vo1-0.4 4.7 Vo1-0.1 V

Rt

Reset Threshold Hysteresis 50 100 200 mV

Rth

Reset Pulse Delay
Reset Reaction Time CT= 100nF 1 10 50
Reset Output LOW Voltage

RL

Reset Output HIGH Leakage V
Delay Comparator Threshold 2.0 V
Delay Comparator Threshold

Hysteresis

1:V

connected to ADJ.VO2canbe set to higher values by inserting an external resistordivider.

O2

2 : Foldback characteristic

= 100nF; tR> 100µs

C

T

= 10KΩto V01V

R

RES

=5V 1

RES

1.5V

≥

S

55 100 180 ms

100 mV

The typicalcurve of the standby outputvoltage as
afunctionof theinputsupplyvoltageis shownin fig.

1.
The current consumptionof the device (quiescent

current) is less than 250µA when output 2 is dis­abled(standbymode).The dropoutvoltage is con­trolled to reduce the quiescent current peak in the
undervoltage regionand to improve the transient
responsein this region.

Thequiescentcurrentisshowninfig.2 asafunction
of thesupplyinput voltage2.

OUTPUT2 VOLTAGE
Theoutput2 regulatorusesthe same outputstruc-

tureas thestandbyregulator,butratedforanoutput
currentof 500mA.

Theoutput 2 regulatorworks in trackingmode with
the standbyoutputvoltageas a referencevoltage.

The output 2 regulator can be switched off via the
Enableinput.

0.4 V

generatedby overvoltagepulses.

s

µ

A

µ

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L4937N

Figure1 : OutputVoltagevs. InputVoltage.

Figure2 : QuiescentCurrent vs.SupplyVoltage.

400

200

RESETCIRCUIT
Theblockcircuitdiagramof theresetcircuitisshown

infig.3.Theresetcircuitsupervisesthestandbyout­put voltage. The reset threshold of 4.7V is defined
by the internal reference voltage and the standby
outputdivider.

The reset pulse delay time t
chargetime ofan externalcapacitorC

C

x2V

T

=

t

RD

2µA

, is defined by the

RD

:

T

Thereactiontimeof theresetcircuitdependsonthe
discharge time limitation of the reset capacitor C
and isproportionalto thevalue of CT.

The reactiontime of the reset circuit increasesthe
noiseimmunity.Infact,ifthestandbyoutputvoltage
drops below the reset threshold for a time shorter
thanthe reactiontimet

, noreset outputvariation

RR

occurs. The nominal reset delay is generated for
standbyoutputvoltage drops longer than the time
necessaryfor the complete discharging of the ca­pacitorC

. This timeis typicallyequalto 50µsifC

T

= 100nF. The typical reset output waveforms are
shownin fig.

T

T

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L4937N

Figure3 :

Figure4 :

BlockDiagramof theReset Circuit.

TypicalReset OutputWaveforms.

VRT

VOUT1

+0.2V

VRT

1.5V

RESET

t

RD

VINPUT

VOUT1

t

RR

t

R

t

RD

D95AT216

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L4937N

DIM.

MIN. TYP. MAX. MIN. TYP. MAX.

A 4.8 0.189
C 1.37 0.054
D 2.4 2.8 0.094 0.110

D1 1.2 1.35 0.047 0.053

E 0.35 0.55 0.014 0.022

E1 0.7 0.97 0.028 0.038

F 0.6 0.8 0.024 0.031

F1 0.9 0.035

G 2.34 2.54 2.74 0.095 0.100 0.105
G1 4.88 5.08 5.28 0.193 0.200 0.205
G2 7.42 7.62 7.82 0.295 0.300 0.307
H2 10.4
H3 10.05 10.4 0.396 0.409

L 16.7 16.9 17.1 0.657 0.668 0.673
L1 14.92
L2 21.24 21.54 21.84 0.386 0.848 0.860
L3 22.27 22.52 22.77 0.877 0.891 0.896
L4 1.29
L5 2.6 2.8 3 0.102 0.110 0.118
L6 15.1 15.5 15.8 0.594 0.610 0.622
L7 6 6.35 6.6 0.236 0.250 0.260
L9 0.2 0.008

M 2.55 2.8 3.05 0.100 0.110 0.120

M1 4.83 5.08 5.33 0.190 0.200 0.210

V4 40° (typ.)

Dia 3.65 3.85 0.144 0.152

mm inch

0.409

0.587

0.051

OUTLINE AND

MECHANICAL DATA

Heptawatt V

H3

L

VV

E

L1

M1

A

C

D

M

D1

H2

V4

L9

H1

L5

Dia.

L2
L3

F

E1

E

GG1G2

F

L7

L4

L6

F1H2

HEPTAMEC

8/9

L4937N

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license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this
publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMi­croelectronics products are not authorized for use as critical components in life support devices or systems without express written
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