Page 1
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.
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FUNCTION
Page 3
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
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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
Page 5
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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L4962
Figure3. Test and applicationcircuit (Powerdip)
1) D1: BYW98 or 3A Schottky diode, 45V of VRRM;
2) L
: CORE TYPE- MAGNETICS 58120 - A2 MPP
1
N° TURNS 45, WIRE GAUGE: 0.8mm (20 AWG)
3) C
: ROE, EKR 220µF 40V
6,C7
Figure 4. Quiescent drain
currentvs.supplyvoltage (0%
duty cycle)
6/15
Figure 5. Quiescent drain
current vs. supply voltage
(100% duty cycle)
Figure 6. Quiescent drain
current vs. junct ion temperature(0% duty cycle)
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L4962
Figure 7. Quiescent drain
current vs. junction temperature(100% duty cycle)
Figure 10. Open loop frequency and phase re- sponse
of error amplifier
Figure 8. Reference voltage
(pin 10)vs. V
rdip) vs. V
i
i
Figure 11. Sw itchi ng frequency vs. inputvoltage
Figure 9. Reference voltage
(pin 10 ) vs. junction t emperature
Figure 1 2. Swit ching frequenc y vs . ju nction te mperature
Figure 13 . S witching f requencyvs. R2 (seetestcircuit)
Figure 14 . Li ne tran sie nt
response
Figure 15 . Load transient
response
7/15
Page 8
L4962
Fig ur e 16 . S u pply vol t a ge
ripple rejectionvs. frequency
Figure 19. Efficien cy vs.
output current
Figure 17. Dropout voltage
between pin 7 and pin 2 vs.
current at pin 2
Figure 20. Efficiency vs.
output current
Figure 18. Dropout voltage
between pin 7 and 2 v s.
junction temperature
Figure 21. Efficiency vs.
output current
Figure 22 . Effici ency vs.
outputvoltage
8/15
Figure 23. Efficiency vs.
output voltage
Figure 24. Maximum allowable powerdissipationvs.ambient temperature (Powerdip)
Page 9
APPLICATION INFORMATION
Figure25. Typical application circuit
C1,C6,C7: EKR (ROE)
D
: BYW98 OR VISK340 (SCHOTTKY)
1
SUGGESTED INDUCTORS: (L
COGEMA 946043
OR U15, GUP15, 60 TURNS 1mm, AIRGAP 0.8mm (20AWG) - COGEMA969051.
) = MAGNETICS 58120 - A2MPP- 45 TURNS - WIRE GAUGE 0.8mm(20AWG)
1
L4962
Figure26. P.C.boardand component layout of the circuit of Fig. 25 (1 : 1 scale)
Resistor valuesfor
standard output 7 voltages
V
12V
15V
18V
24V
o
R3 R4
4.7KΩ
4.7KΩ
4.7KΩ
4.7KΩ
6.2KΩ
9.1KΩ
12KΩ
18KΩ
9/15
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L4962
APPLICATION INFORMATION (continued)
Figure 27. - Aminimal 5.1Vfixedregulator; Very few component arerequired
* COGEMA946043 (TOROID CORE)
** EKR (ROE)
969051 (U15 CORE)
Figure28. Programmablepowersupply
Vo= 5.1Vto 15V
I
= 1.5A max
o
Load regulation(0.5Ato 1.5A) =10mV (V
Line regulation(220V ± 15% and to I
= 5.1V)
o
= 1A)= 15mV (Vo= 5.1V)
o
10/15
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L4962
APPLICATION INFORMATION (continued)
Figure29. DC-DC converter 5.1V/4A, ± 12V/1A.A suggestionhow to synchronize a negativeoutput
L1, L3 = COGEMA 946043(969051)
L2 =COGEMA 946044 (946045)
Figure30. Inmultiple suppliesseveral
L4962s can be synchronizedas shown
Figure 31. Preregulator for distributedsupplies
* L2 and C2 are necessary to reduce the switchingfrequency spikes
when linear regulators are remote from L4962
11/15
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L4962
MOUNTING INSTRUCTION
The Rth-j-amb of the L4962 can be reduced by
solderingtheGND pinsto a suitablecopperareaof
the printed circuit board(Fig. 32).
The diagram of figure 33 shows the R
th-j-amb
functionof the side ”l” of two equal squarecopper
areashavingthethicknessof35µ(1.4mils).During
as a
soldering the pins temperature must not exceed
260°C and the soldering time must not be longer
than 12 seconds.
The externalheatsink orprinted circuit copper are
must beconnectedto electrical ground.
Figure32.ExampleofP.C.boardcopperareawhichisused
as heatsink
Figure 33. Maximum dissipable
power and junction to ambient
thermal resistancevs. side”l”
12/15
Page 13
POWERDIPPACKAGE MECHANICAL DATA
L4962
DIM.
MIN. TYP. MAX. MIN. TYP. MAX.
a1 0.51 0.020
B 0.85 1.40 0.033 0.055
b 0.50 0.020
b1 0.38 0.50 0.015 0.020
D 20.0 0.787
E 8.80 0.346
e 2.54 0.100
e3 17.78 0.700
F 7.10 0.280
I 5.10 0.201
L 3.30 0.130
Z 1.27 0.050
mm inch
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L4962
HEPTAWATT PACKAGE MECHANICAL DATA
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
F 0.6 0.8 0.024 0.031
F1 0.9 0.035
G 2.41 2.54 2.67 0.095 0.100 0.105
G1 4.91 5.08 5.21 0.193 0.200 0.205
G2 7.49 7.62 7.8 0.295 0.300 0.307
H2 10.4 0.409
H3 10.05 10.4 0.396 0.409
L 16.97 0.668
L1 14.92 0.587
L2 21.54 0.848
L3 22.62 0.891
L5 2.6 3 0.102 0.118
L6 15.1 15.8 0.594 0.622
L7 6 6.6 0.236 0.260
M 2.8 0.110
M1 5.08 0.200
Dia 3.65 3.85 0.144 0.152
mm inch
14/15
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L4962
Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the
consequences of use of such informationnor for any infringement of patents or other rights of third parties which may result from itsuse. No
license is granted by implication orotherwise under anypatent or patent rights ofSGS-THOMSON Microelectronics. Specifications mentioned
in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied.
SGS-THOMSON Microelectronicsproducts arenotauthorized foruseas critical components inlife support devices orsystems without express
written approval of SGS-THOMSON Microelectronics.
1996 SGS-THOMSON Microelectronics -AllRights Reserved
SGS-THOMSON Microelectronics GROUP OF COMPANIES
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15/15
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