ST MICROELECTRONICS L 4962 TUBE Datasheet

1.5APOWER SWITCHING REGULATOR

1.5AOUTPUTCURRENT

5.1VTO 40V OUTPUTVOLTAGERANGE
PRECISE(± 2%)ON-CHIP REFERENCE
HIGHSWITCHINGFREQUENCY
VERYHIGH EFFICIENCY (UPTO90%)
VERYFEW EXTERNALCOMPONENTS
SOFTSTART
INTERNALLIMITINGCURRENT
THERMAL SHUTDOWN

DESCRIPTION

The L4962is a monolithicpowerswitchingregula­tor delivering1.5Aat a voltagevariable from 5V to
40Vin stepdown configuration.

Featuresof the device include current limiting, soft
start,thermal protection and 0 to100% dutycycle
for continuousoperating mode.

L4962

POWERDIP

(12 +2 + 2)

ORDERING NUMBERS : L4962/A(12+2+2Powerdip)

L4962E/A (Heptawatt)
L4962EH/A (Horizontal

TheL4962ismountedina16-leadPowerdipplastic
packageandHeptawattpackageand requiresvery
few external components.

Efficient operation at switching frequencies up to
150KHz allows a reduction in the size and costof
externalfilter components.

HEPTAWATT

Heptawatt)

BLOCK DIAGRAM

March 1996

Pin X = Powerdip
Pin (X) = Heptawatt

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L4962

ABSOLUTEMAXIMUM RATINGS

Symbol Parameter Value Unit

Inputvoltage 50 V

7

Inputto output voltage difference 50 V
Negativeoutput DC voltage -1 V

2

V

7-V2

V

V

Output peak voltage at t = 0.1µs; f =100KHz -5 V

V

11,V15

V

P

T

j,Tstg

I
I

Voltageat pin 11,15 5.5 V
Voltageat pin 10 7 V

10

Pin 11 sink current 1 mA

11

Pin 14 sourcecurrent 20 mA

14

Power dissipation atT

tot

Junctionand storage temperature -40 to 150 °C

PIN CONNECTION (Top view)

≤ 90°C (Powerdip)

pins

T

≤ 90°C (Heptawatt)

case

4.3
15

W
W

THERMAL DATA

Symbol Parameter Heptawatt Powerdip

R

th j-case

R

th j-pins

R

th j-amb

* Obtained with the GND pins soldered to printed circuit with minimized copperarea.

Thermal resistancejunction-case max 4°C/W ­Thermal resistancejunction-pins max - 14°C/W
Thermal resistancejunction-ambient max 50°C/W 80°C/W*

PIN FUNCTIONS

HEPTAWATT POWERDIP NAME

1 7 SUPPLYVOLTAGE Unregulated voltage input. An internal regulator powers

the internal logic.

2 10 FEEDBACK INPUT The feedbackterminal of the regulationloop.Theoutput

is connected directly to this terminal for 5.1V operation;
it is connected via adivider for higher voltages.

3 11 FREQUENCY

COMPENSATION

A series RC network connected between this terminal
and ground determines the regulation loop gain
characteristics.

2/15

FUNCTION

PIN FUNCTIONS (cont’d)

L4962

HEPTAWATT POWERDIP NAME

FUNCTION

4 4, 5, 12,13 GROUND Common groundterminal.

5 14 OSCILLATOR A parallel RC network connected to this terminal

determines the switching frequency. This pin must be
connected to pin 7 input when the internal oscillator is
used.

6 15 SOFT START Soft start time constant. A capacitor is connected

between this terminaland ground to define the soft start
time constant. This capacitor also determines the
average short circuitoutput current.

7 2 OUTPUT Regulator output.

1, 3,6,

N.C.

8, 9, 16

ELECTRICAL CHARACTERISTICS (Refer to the test circuit, Tj=25°C, Vi= 35V, unless otherwise
specified)

Symbol Parameter Test Conditions Min. Typ. Max. Unit

DYNAMIC CHARACTERISTICS

V

Output voltage range Vi= 46V Io=1A V

o

V

∆ V
∆V

V

ref

Input voltage range Vo=V

i

Line regulation Vi= 10V to 40V Vo=V

o

Load regulation Vo=V

o

Internal reference voltage

Vi= 9Vto 46V Io= 1A 5 5.1 5.2 V

to 36V Io= 1.5A 9 46 V

ref

ref

(pin 10)

∆

V

ref

∆ T

V

I

om

I

2L

I

SH

Average temperature
coefficient of refer.voltage

Dropout voltage Io= 1.5A 1.5 2 V

d

Maximum operatingload
current

Current limiting threshold
(pin 2)

Input average current Vi= 46V; output short-circuit 15 30 mA

T

=0°C to 125°C

j

I

=1A

o

Vi= 9Vto 46V
V

o=Vref

to 36V

Vi= 9Vto 46V

o=Vref

to 36V

V

η Efficiency f = 100KHz V

I

=1A Vo= 12V 80 %

o

SVR Supply voltage ripple

rejection

∆ V

fripple

V

o=Vref

=2V

i

= 100Hz

rms

ref

=1A 15 50 mV

refIo

40 V

Io= 0.5A to 1.5A 8 20 mV

0.4 mV/°C

1.5 A

2 3.3 A

o=Vref

70 %

50 56 dB

Io = 1A

3/15

L4962

ELECTRICALCHARACTERISTICS (continued)

Symbol Parameter Test Conditions Min. Typ. Max. Unit

DYNAMICCHARACTERISTICS (cont’d)

f Switching frequency 85 100 115 KHz

∆

f

Voltagestability of
switching frequency

V

∆

i

∆ f

Temperature stability of

∆

switching frequency

T

j

Vi= 9V to46V 0.5 %

Tj=0°C to 125°C1%

f

Maximum operating

max

switching frequency

T

Thermal shutdown

sd

junction temperature

DC CHARACTERISTICS

I

-I

Quiescent draincurrent 100% duty cycle

7Q

Output leakage current 0% duty cycle 1 mA

2L

SOFTSTART

I

15SO

I

Source current 100 140 180 µA
Sink current 50 70 120 µA

15SI

ERROR AMPLIFIER

V

V

I

High level output voltage V10= 4.7V I11= 100µA 3.5 V

11H

Low level output voltage V10= 5.3V I11= 100µA 0.5 V

11L

Sink output current V10= 5.3V 100 150 µA

11SI

Vo=V

ref

Io= 1A 120 150 KHz

150 °C

30 40 mA

pins 2and 14 open

V

= 46V

i

0% duty cycle 15 20 mA

-I

Source outputcurrent V10= 4.7V 100 150 µA

11SO

I

Input bias current V10= 5.2V 2 10 µA

10

DC openloop gain V11=1Vto3V 46 55 dB

G

v

OSCILLATOR

-I

4/15

Oscillator source current 5 mA

14

CIRCUITOPERATION(refertothe block diagram)
TheL4962 isamonolithic stepdownswitchingregu-

latorprovidingoutputvoltagesfrom5.1Vto40Vand
delivering1.5A.

The regulation loop consists of a sawtoothoscilla­tor, error amplifier, comparator and the output
stage.An errorsignalisproducedby comparingthe
output voltage with a precise 5.1V on-chip refer­ence (zener zap trimmedto ±2%).

Thiserrorsignalisthencomparedwiththesawtooth
signal to generate the fixedfrequency pulse width
modulatedpulseswhich drive the output stage.

Thegain and frequencystabilityof theloopcan be
adjusted by an external RC network connected to
pin 11. Closing the loop directly gives an output
voltage of 5.1V. Higher voltages are obtained by
inserting a voltage divider.

Outputovercurrentsat switchon are prevented by
the soft start function.The error amplifier output is
initiallyclamped by the external capacitor Cssand

L4962

allowedtorise,linearly,asthiscapacitoris charged
by aconstantcurrentsource.Output overload pro­tection is provided in the form of a current limiter.
The load current is sensed by an internal metal
resistorconnectedto a comparator. When the load
currentexceedsapresetthresholdthis comparator
sets a flipflop whichdisablesthe outputstage and
dischargesthe soft start capacitor. A second com­parator resets the flipflop when thevoltageacross
the soft start capacitorhas fallento 0.4V.

The output stage isthus re-enabledand the output
voltagerisesundercontrolof thesoftstart network.
If the overload condition is still present the limiter
will trigger again when the threshold current is
reached.Theaverageshort circuitcurrent is limited
to a safevalue by the dead time introduced by the
soft start network.Thethermaloverloadcircuit dis­ables circuit operation when the junction tempera­ture reaches about 150°C and has hysteresis to
prevent unstable conditions.

Figure1. Softstart waveforms

Figure2. Current limiter waveforms

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