SGS Thomson Microelectronics L296-P, L296 Datasheet

L296

L296P

April1993

HIGH CURRENT SWITCHING REGULATORS

.4 A OUTPUT CURRENT

.5.1 V TO 40 V OUTPUT VOLTAGERANGE

.0 TO 100 % DUTY CYCLERANGE

.PRECISE(±2 %) ON-CHIPREFERENCE

.SWITCHINGFREQUENCYUP TO200KHz

.VERY HIGHEFFICIENCY(UPTO 90%)

.VERY FEWEXTERNAL COMPONENTS

.SOFT START

.RESETOUTPUT

.EXTERNALPROGRAMMABLE LIMITING

CURRENT (L296P)

.CONTROLCIRCUITFOR CROWBAR SCR

.INPUT FOR REMOTE INHIBIT AND

SYNCHRONUSPWM

.THERMALSHUTDOWN

DESCRIP TION

TheL296andL296Parestepdownpowerswitching
regulatorsdelivering4 Aat a voltage variablefrom

5.1 Vto40 V.
Featuresof thedevicesincludesoftstart,remotein-

hibit, thermal protection, a reset output for micro­processors and a PWM comparatorinput for syn­chronizationin multichip configurations.

TheL296Pincudesexternalprogrammablelimiting
current.

TheL296 andL296Paremountedina15-leadMul­tiwattplasticpowerpackageandrequiresveryfew
externalcomponents.

Efficient operation at switching frequencies up to
200 KHz allows a reductionin the size and costof
external filter components. A voltage sense input
and SCR drive output are provided for optional
crowbar overvoltage protection with an external
SCR.

Multiwatt



(15 lead)

ORDE RING NUM BERS :

L296 (Vertical) L296HT (Hor izontal)
L296P ( Vertical) L296PHT ( H ori zont a l)

PIN CONNE CTION (top view)

1/21

PIN FUNCTIONS

N° Name Function

1 CROWBAR INPUT Voltage Sense Input for Crowbar Overvoltage Protection. Normally connected to the

feedback input thus triggering the SCR when V

out

exceeds nominal by 20 %. May
also monitor the input and a voltage divider can be added to increase the threshold.
Connected to ground when SCR not used.

2 OUTPUT Regulator Output
3 SUPPLY VOLTAGE Unrergulated Voltage Input. An internal Regulator Powers the L296s Internal Logic.
4 CURRENT LIMIT A resistor connected between this terminal and ground sets the current limiter

threshold. If this terminal is left unconnected the threshold is internally set (see
electrical characteristics).

5 SOFT START Soft Start Time Constant. A capacitor is connected between this terminal and ground

to define the soft start time constant. This capacitor also determines the average
short circuit output current.

6 INHIBIT INPUT TTL – Level Remote Inhibit. A logic high level on this input disables the device.
7 SYNC INPUT Multiple L296s are synchronized by connecting the pin 7 inputs together and omitting

the oscillator RC network on all but one device.

8 GROUND Common Ground Terminal
9 FREQUENCY

COMPENSATION

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

10 FEEDBACK INPUT The Feedback Terminal on the Regulation Loop. The output is connected directly to

this terminal for 5.1V operation ; it is connected via a divider for higher voltages.

11 OSCILLATOR A parallel RC networki connected to this terminal determines the switching frequency.

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

12 RESET INPUT Input of the Reset Circuit. The threshold is roughly 5 V. It may be connected to the

feedback point or via a divider to the input.

13 RESET DELAY A capacitor connected between this terminal and ground determines the reset signal

delay time.

14 RESET OUTPUT Open collector reset signal output. This output is high when the supply is safe.
15 CROWBAR OUTPUT SCR gate drive output of the crowbar circuit.

BLOCK DIAGRAM

L296 - L296P

2/21

CIRCUIT OPERATION

(refer to the block diagram)
The L296 and L296P are monolithic stepdown

switchingregulatorsprovidingoutputvoltagesfrom

5.1Vto40Vand delivering 4A.
Theregulationloopconsistsofasawtoothoscillator,

erroramplifier,comparatorandtheoutputstage.An
error signal is produced by comparing the output
voltagewitha precise5.1Von-chipreference(zener
zaptrimmedto± 2%).Thiserrorsignalis thencom­paredwiththesawtoothsignalto generatethefixed
frequencypulsewidthmodulatedpulseswhichdrive
theoutputstage.Thegainandfrequencystabilityof
theloopcanbeadjustedbyan externalRC network
connectedtopin9.Closingtheloopdirectlygivesan
outputvoltageof5.1V.Highervoltagesareobtained
byinsertinga voltagedivider.

Outputovercurrentsat switchon are preventedby
the soft start function. The error amplifier outputis
initially clampedby the externalcapacitorCss and
allowedtorise, linearly,as thiscapacitorischarged
bya constantcurrentsource.

Outputoverloadprotectionis providedintheformof
a currentlimiter. The load currentis sensed by an
internalmetal resistor connectedto a comparator.
Whenthe load current exceedsa preset threshold
this comparator sets a flip flop which disables the
outputstageanddischargesthesoftstartcapacitor.
A second comparator resets the flip flop when the
voltageacrossthe soft startcapacitorhas fallen to

0.4V.The output stage is thus re-enabled and the
output voltage rises under control of the soft start
network.If theoverloadconditionis stillpresentthe
limiterwill triggeragainwhen the thresholdcurrent
isreached.The averageshort circuit current islim­itedtoa safe valueby the deadtimeintroduced by
the softstart network.

The reset circuit generatesan output signal when
the supply voltage exceeds a threshold pro­grammed byan externaldivider.The resetsignalis
generatedwitha delay timeprogrammedby an ex­ternal capacitor. When the supply falls below the
threshold the reset output goes low immediately.
Theresetoutputis an opencollector.

Thescrowbarcircuit sensestheoutput voltageand
the crowbaroutputcan providea currentof 100mA
toswitchon anexternalSCR. ThisSCRis triggered
when the output voltage exceeds the nominal by
20%. There is no internalconnection between the
outputandcrowbarsense inputthereforethe crow­bar canmonitor eitherthe input or the output.

ATTL-levelinhibitinputisprovidedforapplications
suchasremoteon/offcontrol.Thisinputisactivated
byhigh logiclevelanddisablescircuitoperation.Af­ter an inhibit the L296 restartsunder controlof the
soft startnetwork.

Thethermaloverloadcircuit disablescircuit opera­tion when the junctiontemperaturereachesabout
150 °Candhas hysteresisto preventunstablecon-
ditions.

Figure 1 : ResetOutput Waveforms

L296 - L296P

3/21

Figure 2 : SoftStartWaveforms

Figure 3 : CurrentLimiter Waveforms

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

i

Input Voltage (pin 3) 50 V

V

i–V2

Input to Output Voltage Difference 50 V

V

2

Output DC Voltage
Output Peak Voltage at t = 0.1 µsec f = 200KHz

–1

–7

V
V

V

1,V12

Voltage at Pins 1, 12 10 V

V

15

Voltage at Pin 15 15 V

V

4,V5,V7,V9,V13

Voltage at Pins 4, 5, 7, 9 and 13 5.5 V

V

10,V6

Voltage at Pins 10 and 6 7 V

V

14

Voltage at Pin 14 (I14≤ 1 mA) V

i

I

9

Pin 9 Sink Current 1 mA

I

11

Pin 11 Source Current 20 mA

I

14

Pin 14 Sink Current (V14< 5 V) 50 mA

P

tot

Power Dissipation at T

case

≤ 90 °C20W

T

j

,T

stg

Junction and Storage Temperature – 40 to 150 °C

L296 - L296P

4/21

THERMAL DATA

Symbol Parameter Value Unit

R

th j-case

Thermal Resistance Junction-case Max. 3 °C/W

R

th j-amb

Thermal Resistance Junction-ambient Max. 35 °C/W

ELECTRICAL CHARACTERISTICS

(refer to the test circuits T

j

=25oC, Vi= 35V, unless otherwise specified)

Symbol Parameter Test Conditions Min. Typ. Max. Unit Fig.

DYNAMIC CHARACTERISTICS (pin 6 to GND unless otherwise specified)

V

o

Output Voltage Range Vi= 46V, Io=1A V

ref

40 V 4

V

i

Input Voltage Range Vo=V

ref

to 36V, Io≤ 3A 9 46 V 4

V

i

Input Voltage Range Note (1), Vo=V

REF

to 36V Io=4A 46 V 4

∆V

o

Line Regulation Vi=10V to 40V, Vo=V

ref,Io

=2A 15 50 mV 4

∆V

o

Load Regulation Vo=V

ref

Io=2Ato4A
I

o

= 0.5A to 4A

101530

45

mV 4

V

ref

Internal Reference Voltage (pin 10) Vi= 9V to 46V, Io= 2A 5 5.1 5.2 V 4

∆ V

ref

∆ T

Average Temperature Coefficient
of Reference Voltage

T

j

=0°C to 125°C, Io= 2A 0.4 mV/°C

V

d

Dropout Voltage Between Pin 2
and Pin 3

Io=4A
I

o

=2A

2

1.3

3.2

2.1

V
V

4
4

I

2L

Current Limiting Threshold (pin 2) L296 - Pin 4 Open,

V

i

= 9V to 40V, Vo=V

ref

to 36V

4.5 7.5 A 4

L296P - V

i

= 9V to 40V, Vo=V

ref

Pin 4 Open
R

Iim

= 22kΩ

5

2.5

7

4.5

A4

I

SH

Input Average Current Vi= 46V, Output Short-circuited 60 100 mA 4

η Efficiency I

o

=3A

V

o=Vref

Vo= 12V

75
85

%4

SVR Supply Voltage Ripple Rejection ∆V

i

=2V

rms,fripple

= 100Hz

V

o=Vref,Io

=2A

50 56 dB 4

f Switching Frequency 85 100 115 kHz 4

∆ f

∆ V

i

Voltage Stability of Switching
Frequency

Vi= 9V to 46V 0.5 % 4

∆ f

∆ T

j

Temperature Stability of Switching
Frequency

Tj=0°C to 125°C1%4

f

max

Maximum Operating Switching
Frequency

Vo=V

ref,Io

= 1A 200 kHz –

T

sd

Thermal Shutdown Junction
Temperature

Note (2) 135 145 °C–

DC CHARACTERISTICS

I

3Q

Quiescent Drain Current Vi= 46V, V7= 0V, S1 : B, S2 : B

V

6

=0V

V

6

=3V

66
30

85
40

mA

–I

2L

Output Leakage Current Vi= 46V, V6= 3V, S1 : B, S2 : A,

V

7

=0V

2mA

Note (1) : Using min. 7 A schottky diode.

(2) :Guaranteed by design,not 100% tested inproduction.

L296 - L296P

5/21

ELECTRICAL CHARACTERISTICS (continued)

Symbol Parameter Test Conditions Min. Typ. Max. Unit Fig.

SOFT START

I

5so

Source Current V6= 0V, V5= 3V 80 130 150 µA6b

I

5si

Sink Current V6= 3V, V5= 3V 50 70 120 µA6b

INHIBIT

V

6L

V

6H

Input Voltage

Low Level
High Level

V

i

= 9V to 46V, V7= 0V,

S1 : B, S2 : B – 0.3

2

0.8

5.5

V6a

–I

6L

–I

6H

Input Current
with Input Voltage

Low Level
High Level

V

i

= 9V to 46V, V7= 0V,

S1 : B, S2 : B

V

6

= 0.8V

V

6

=2V

10

3

µA6a

ERROR AMPLIFIER

V

9H

High Level Output Voltage V10= 4.7V, I9= 100µA,

S1 : A, S2 : A

3.5 V 6c

V

9L

Low Level Output Voltage V10= 5.3V, I9= 100µA,

S1 : A, S2 : E

0.5 V 6c

I

9si

Sink Output Current V10= 5.3V, S1 : A, S2 : B 100 150 µA6c

–I

9so

Source Output Current V10= 4.7V, S1 : A, S2 : D 100 150 µA6c

I

10

Input Bias Current V10= 5.2V, S1 : B

V

10

= 6.4V, S1 : B, L296P

2
2

10
10

µAµA6c

6c

G

v

DC Open Loop Gain V9= 1V to 3V, S1 : A, S2 : C 46 55 dB 6c

OSCILLATOR AND PWM COMPARATOR

–I

7

Input Bias Current of
PWM Comparator

V7= 0.5V to 3.5V 5 µA6a

–I

11

Oscillator Source Current V11= 2V, S1 : A, S2 : B 5 mA

RESET

V

12 R

Rising Threshold Voltage

V

i

= 9V to 46V,

S1 : B, S2 : B

V

ref

-150mV

V

ref

-100mV

V

ref

-50mV

V6d

V

12 F

Falling Threshold Voltage 4.75 V

ref

-150mV

V

ref

-100mV

V6d

V

13 D

Delay Thershold Voltage

V

12

= 5.3V, S1 : A, S2 : B

4.3 4.5 4.7 V 6d

V

13 H

Delay Threshold Voltage
Hysteresis

100 mV 6d

V

14 S

Output Saturation Voltage I14= 16mA, V12= 4.7V, S1, S2 : B 0.4 V 6d

I

12

Input Bias Current V12=0VtoV

ref

,S1:B,S2:B 1 3 µA6d

–I

13 so

I

13 si

Delay Source Current
Delay Sink Current

V

13

= 3V, S1 : A, S2 : B

V

12

= 5.3V

V

12

= 4.7V

70
10

110 140 µA

mA

6d

I

14

Output Leakage Current Vi= 46V, V12= 5.3V, S1 : B, S2 : A 100 µA6d

CROWBAR

V

1

Input Threshold Voltage S1 : B 5.5 6 6.4 V 6b

V

15

Output Saturation Voltage Vi= 9V to 46V, Vi= 5.4V,

I

15

= 5mA, S1 : A

0.2 0.4 V 6b

I

1

Input Bias Current V1= 6V, S1 : B 10 µA6b

–I

15

Output Source Current Vi= 9V to 46V, V1= 6.5V,

V

15

= 2V, S1 : B

70 100 mA 6b

L296 - L296P

6/21

Figure 4 : DynamicTest Circuit

C7,C8 : EKR(ROE)
L1 :L = 300 µH at8 A Coretype : MAGNETICS 58930 - A2 MPP

N°turns : 43 Wire Gauge :1 mm (18 AWG) COGEMA 946044

(*) Minimumsuggested value(10 µF) to avoid oscillations.Ripple consideration leads to typicalvalueof 1000 µF or higher.

Figure 5 : PC.Board and Component Layoutof the Circuit of Figure 4 (1:1scale)

L296 - L296P

7/21