© Semiconductor Components Industries, LLC, 2006

July, 2006 − Rev. 31 Publication Order Number:

UA78S40/D

UA78S40

Universal SwitchingRegulator Subsystem

The �A78S40 is a switching regulator subsystem, consisting of atemperature compensated voltage reference, controlled−duty cycleoscillator with an active current limit circuit, comparator, high−currentand high−voltage output switch, capable of 1.5 A and 40 V, pinned−outpower diode and an uncommitted operational amplifier, which can bepowered up or down independent of the IC supply. The switchingoutput can drive external NPN or PNP transistors when voltagesgreater the 40 V, or currents in excess of 1.5 A, are required. Some ofthe features are wide−supply voltage range, low standby current, highefficiency and low drift. The �A78S40 is available in commercial(0° to + 70°C), and automotive (−40° to + 85°C) temperature ranges.

Some of the applications include use in step−up, step−down, andinverting regulators, with extremely good results obtained in battery−operated systems.• Output Adjustable from 1.25 V to 40 V

• Peak Output Current of 1.5 A Without External Transistor

• 80 dB Line and Load Regulation

• Operation from 2.5 V to 40 V Supply

• Low Standby Current Drain

• High Gain, High Output Current, Uncommitted Op Amp

Figure 1. Simplified Block Diagram

CT Ipk

Oscillator

−

+Comp.

−

+

Op1.25V

Reference

S

R

Q

170

8

(Bottom View)

RefOutput

Output

9

D1

InvInput

NoninvInput

VCCOp Amp

SwitchEmitter

DiodeAnode

DiodeCathode

Noninv.Input

Inv.Input Gnd

TimingCapacitor VCC

IpkSense

DriverCollector

SwitchCollector

7 6 5 4 3 2 1

10 11 12 13 14 15 16

Amp

NOTE: This device contains 84 activetransistors.

Device Package Shipping

ORDERING INFORMATION

�A78S40PC PDIP−16 25 Units/Rail

PDIP−16P SUFFIXCASE 648

16

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�A78S40PV PDIP−16 25 Units/Rail

MARKINGDIAGRAM

x = C or VA = Assembly LocationWL = Wafer LotYY = YearWW = Work Week

1

PIN CONNECTIONS

11

5

2

1

9

10

12

13

14

15

16

8

7

6

4

3

(Top View)

Diode Anode

Reference

Inv. Input

Noninv.

VCC Op Amp

Op Amp Output

Switch Emitter

Diode Cathode

OpAmp

ComparatorNoninv. Input

ComparatorInv. Input

Ground

Timing Capacitor

VCC

Ipk Sense

Driver Collector

Switch Collector

1

16

UA78S40PxAWLYYWW

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MAXIMUM RATINGS

Rating Symbol Value Unit

Power Supply Voltage VCC 40 V

Op Amp Power Supply Voltage VCC (Op Amp) 40 V

Common Mode Input Range(Comparator and Op Amp)

VICR −0.3 to VCC V

Differential Input Voltage (Note 2) VID ± 30 V

Output Short Circuit Duration (Op Amp) Continuous −

Reference Output Current Iref 10 mA

Voltage from Switch Collectors to Gnd 40 V

Voltage from Switch Emitters to Gnd 40 V

Voltage from Switch Collectors to Emitter 40 V

Voltage from Power Diode to Gnd 40 V

Reverse−Power Diode Voltage VDR 40 V

Current through Power Switch ISW 1.5 A

Current through Power Diode ID 1.5 A

Power Dissipation and Thermal Characteristics:Plastic Package (TA = + 25°C)

Derate above + 25°C (Note 1)PD

1/R�JA

150014

mWmW/°C

Storage Temperature Range Tstg −65 to + 150 °C

Operating Temperature Range�A78S40V�A78S40C

TA−40 to +850 to +70

°C

ELECTRICAL CHARACTERISTICS (VCC = VCC (Op Amp) 5.0 V, TA = Tlow to Thigh, unless otherwise noted.)

Characteristic Symbol Min Typ Max Unit

GENERAL

Supply Voltage VCC 2.5 − 40 V

Supply Current (Op Amp VCC, disconnected)(VCC = 5.0 V)(VCC = 40 V)

ICC−−

1.82.3

3.55.0

mA

Supply Current (Op Amp VCC, connected)(VCC = 5.0 V)(VCC = 40 V)

ICC−−

−−

4.05.5

mA

REFERENCE

Reference Voltage(Iref = 1.0 mA)

Vref 1.180 1.245 1.310 V

Reference Voltage Line Regulation(3.0 V ≤ VCC ≤ 40 V, Iref = 1.0 mA, TA = 25°C)

Regline − 0.04 0.2 mV/V

Reference Voltage Load Regulation(1.0 mA ≤ Iref ≤ 10 mA, TA = 25°C)

Regload − 0.2 0.5 mV/mA

1. Tlow = −40° for �A78S40PV Thigh= +85° for �A78S40PV= 0° for �A78S40PC = +70° for �A78S40PC

2. For supply voltages less than 30 V the maximum differential input voltage (Error Amp and Op Amp) is equal to the supply voltage.

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ELECTRICAL CHARACTERISTICS (VCC = VCC (Op Amp) 5.0 V, TA = Tlow to Thigh, unless otherwise noted.)

Characteristic Symbol Min Typ Max Unit

OSCILLATOR

Charging Current (TA = 25°C)(VCC = 5.0 V)(VCC = 40 V)

Ichg2020

−−

5070

�A

Discharging Current (TA = 25°C)(VCC = 5.0 V)(VCC = 40 V)

Idis150150

−−

250350

�A

Oscillator Voltage Swing (TA = 25°C)(VCC = 5.0 V)

Vosc − 0.5 − V

Ratio of Charge/Discharge Time tchg/tdis − 6.0 − −

CURRENT LIMIT

Current−Limit Sense Voltage (TA = 25°C)(VCC − Vlpk Sense)

VCLS 250 − 350 mV

OUTPUT SWITCH

Output Saturation Voltage 1(ISW = 1.0 A, Pin 15 tied to Pin 16)

Vsat1 − 0.93 1.3 V

Output Saturation Voltage 2(ISW = 1.0 A, I15 = 50 mA)

Vsat2 − 0.5 0.7 V

Output Transistor Current Gain (TA = 25°C)(IC = 1.0 A, VCE = 5.0 V)

hFE − 70 − −

Output Leakage Current (TA = 25°C)(VCE = 40 V)

IC(off) − 10 − nA

POWER DIODE

Forward Voltage Drop (ID = 1.0 A) VD − 1.25 1.5 V

Diode Leakage Current (TA = 25°C) (VDR = 40 V) IDR − 10 − nA

COMPARATOR

Input Offset Voltage (VCM = Vref) VIO − 1.5 15 mV

Input Bias Current (VCM = Vref) IIB − 35 200 nA

Input Offset Current (VCM = Vref) IIO − 5.0 75 nA

Common Mode Voltage Range (TA = 25°C) VICR 0 − VCC − 2.0 V

Power−Supply Rejection Ratio (TA = 25°C)(3.0 ≤ VCC ≤ 40 V)

PSRR 70 96 − dB

OUTPUT OPERATION AMPLIFIER

Input Offset Voltage (VCM = 2.5 V) VIO − 4.0 15 mV

Input Bias Current (VCM = 2.5 V) IIB − 30 200 nA

Input Offset Current (VCM = 2.5 V) IIO − 5.0 75 nA

Voltage Gain + (TA = 25°C)(RL = 2.0 k� to Gnd, 1.0 V ≤ VO ≤ 2.5 V)

AVOL+ 25 250 − V/mV

Voltage Gain − (TA = 25°C)(RL = 2.0 k� to VCC (Op Amp), 1.0 V ≤ VO ≤ 2.5 V)

AVOL− 25 250 − V/mV

Common Mode Voltage Range (TA = 25°C) VICR 0 − VCC − 2.0 V

Common Mode Rejection Ratio (TA = 25°C)(VCM = 0 V to 3.0 V)

CMRR 76 100 − dB

Power−Supply Rejection Ratio (TA = 25°C)(3.0 V ≤ VCC (Op Amp) ≤ 40 V)

PSRR 76 100 − dB

Output Source Current (TA = 25°C) ISource 75 150 − mA

Output Sink Current (TA = 25°C) ISink 10 35 − mA

Slew Rate (TA = 25°C) SR − 0.6 − V/�s

Output Low Voltage (TA = 25°C, IL = −5.0 mA) VOL − − 1.0 V

Output High Voltage (TA = 25°C, IL = 50 mA) VOH VCC(Op Amp)− 3.0

− − V

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Figure 2. Output Switch On/Off Timeversus Oscillator Timing Capacitor

Figure 3. Standby Supply Currentversus Supply Voltage

Figure 4. Emitter−Follower ConfigurationOutput Switch Saturation Voltage

versus Emitter Current

CT, OSCILLATOR TIMING CAPACITOR (nF)

0.1 1.0 10 100

, OU

TP

UT

SW

ITC

H O

N-O

FF

TIM

E (

�s)

μon

-off

tVCC = 5.0 VIpk(sense) = VCC

Pin 10 = GndPin 9 = Vref

ton

toff

VCC, SUPPLY VOLTAGE (V)

0 5.0 10 15 20 25 30 35 40

, SU

PP

LY C

UR

RE

NT

(m

A)

CC

I

CT = 0.001 �FIpk(sense) = VCC

Pin 3 = Gnd

IE, EMITTER CURRENT (A)

, SA

TU

RA

TIO

N V

OLT

AG

E (

V)

CE

(sat

)

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

V

VCC = 5.0 VPins 14, 15, 16 = VCCPins 10, 12 = GndPin 9 = Vref

IC, COLLECTOR CURRENT (A)

, SA

TU

RA

TIO

N V

OLT

AG

E (

V)

CE

(sat

)

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

VVCC = 5.0 VPin 14 = VCCPins 3, 10, 12 = GndPin 9 = Vref

Darlington Connection

Figure 5. Common−Emitter ConfigurationOutput Switch Saturation Voltage

versus Collector Current

1000

100

10

1.0

3.2

2.4

1.6

0.8

0

1.6

1.5

1.4

1.3

1.2

1.1

1.0

1.2

1.0

0.8

0.6

0.4

0.2

0

Forced Beta = 20

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CT Ipk

Oscillator

−

+Comp.

−

+

OpAmp

1.25VReference

S

R

Q

170

12345678

9 10 11 12 13 14 15 16

D1

Vout5.0V/500mA

*L

470+

CO

R2

3.6kR1

1N5822

+100

CT

*Use external rectifier to increase circuit efficiency

1.2k

Vin25V

470pF

RSC0.33

220�H

VCC

Figure 6. Step−Down Converter

CT Ipk

Oscillator

−

+Comp.

−

+

OpAmp

1.25VReference

S

R

Q

170

12345678

9 10 11 12 13 14 15 16

D1

Vout28V/175mA

*

150+

CO

R2

47kR1

1N5822

+100

CT

*Use external rectifier to increase circuit efficiency22k

Vin12V

1500pF

RSC0.22

VCC

Figure 7. Step−Up Converter

170�H

L

180

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CT Ipk

Oscillator

−

+Comp.

−

+

OpAmp

1.25VReference

S

R

Q

170

12345678

9 10 11 12 13 14 15 16

D1

R11.5k

1N5822

+100

CT

Vin15V

1800pF

RSC0.30

50�H L100

Vout−15V/500mA

100 +CO

R218k

VCC

270

D45H8

Figure 8. Inverting Converter

Design Formula Table

fmin

Vin(min) Vsat

Calculation Step−Down Step−Up Inverting

ton

toff

Vout + VF Vout − VF Vin(min) Vout + VF

Vin(min) − Vsat − Vout Vin(min) − Vsat

(ton + toff) maxfmin

I I

CT 4 x 10 5 ton 4 x 10 5 ton 4 x 10 5 ton

Ipk(switch) 2 Iout(max) ton − tofftoff

ton + tofftoff

2 Iout(max) 2 Iout(max)

RSC 0.33 0.33 0.33Ipk(switch) Ipk(switch) Ipk(switch)

L(min)Vin(min) − Vsat − Vout Vin(min) − Vsat Vin(min) − Vsat

ton(max)ton(max) ton(max)

Ipk(switch) Ipk(switch) Ipk(switch)

CO Ipk(switch) (ton + toff) Iout ton

8 Vripple(pp) Vripple

Vsat = Saturation voltage of the output switch. VF = Forward voltage drop of the ringback rectifier.

≈

The following power supply characteristics must be chosen:− Nominal input voltage. If this voltage is not constant, then use Vin(max) for step−down and Vin(min) for step−up and inverting convertor.

− Desired output voltage: Vout = 1.25

− Desired output current.− Minimum desired output switching frequency at the selected values for Vin and IO.− Desired peak−to−peak output ripple voltage. In practice, the calculated value will need to be increased due to the capacitor’s equivalent

series resistance and board layout. The ripple voltage should be kept to a low value since it will directly effect the line and load regulation.

See Application Note AN920 for further information

for step−down and step−up: for inverting.�1 �R2R1� Vout �

1.25 R2R1

Vin

Vout

Ioutfmin

Vripple(pp)

fmin

I

Iout ton

Vripple

≈

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PACKAGE DIMENSIONS

PDIP−16P SUFFIX

CASE 648−08ISSUE R

NOTES:1. DIMENSIONING AND TOLERANCING PER ANSI

Y14.5M, 1982.2. CONTROLLING DIMENSION: INCH.3. DIMENSION L TO CENTER OF LEADS WHEN

FORMED PARALLEL.4. DIMENSION B DOES NOT INCLUDE MOLD FLASH.5. ROUNDED CORNERS OPTIONAL.

−A−

B

F C

S

HG

D

J

L

M

16 PL

SEATING

1 8

916

K

PLANE−T−

MAM0.25 (0.010) T

DIM MIN MAX MIN MAX

MILLIMETERSINCHES

A 0.740 0.770 18.80 19.55

B 0.250 0.270 6.35 6.85

C 0.145 0.175 3.69 4.44

D 0.015 0.021 0.39 0.53

F 0.040 0.70 1.02 1.77

G 0.100 BSC 2.54 BSC

H 0.050 BSC 1.27 BSC

J 0.008 0.015 0.21 0.38

K 0.110 0.130 2.80 3.30

L 0.295 0.305 7.50 7.74

M 0 10 0 10

S 0.020 0.040 0.51 1.01����

ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further noticeto any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liabilityarising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. Alloperating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rightsnor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applicationsintended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. ShouldBuyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates,and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or deathassociated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an EqualOpportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.

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UA78S40/D

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