Device

Operating

Temperature Range

Package

TL494

SEMICONDUCTOR

TECHNICAL DATA

SWITCHMODE

PULSE WIDTH MODULATION

CONTROL CIRCUIT

ORDERING INFORMATION

TL494CN

TL494IN

TA = 0

to +70

TA = 25

to +85

Plastic

PIN CONNECTIONS

Order this document by TL494/D

N SUFFIX

PLASTIC PACKAGE

CASE 648

Ground

Inv

Input

0.1 V

Oscillator

VCC

5.0 V

REF

(Top View)

Noninv
Input

Inv
Input

Vref

Output
Control

VCC

Noninv

Input

Compen/PWN

Comp Input

Deadtime

Control

Error

Amp

Error

Amp

D SUFFIX

PLASTIC PACKAGE

CASE 751B

(SO16)

TL494CD

SO16

MOTOROLA ANALOG IC DEVICE DATA

SWITCHMODE

Pulse Width

Modulation Control Circuit

The TL494 is a fixed frequency, pulse width modulation control circuit

designed primarily for SWITCHMODE power supply control.

Complete Pulse Width Modulation Control Circuitry

OnChip Oscillator with Master or Slave Operation

OnChip Error Amplifiers

OnChip 5.0 V Reference

Adjustable Deadtime Control

Uncommitted Output Transistors Rated to 500 mA Source or Sink

Output Control for PushPull or SingleEnded Operation

Undervoltage Lockout

MAXIMUM RATINGS

(Full operating ambient temperature range applies,

unless otherwise noted.)

Rating

Symbol

TL494C

TL494I

Unit

Power Supply Voltage

VCC

Collector Output Voltage

VC1,

VC2

Collector Output Current

(Each transistor) (Note 1)

IC1, IC2

500

Amplifier Input Voltage Range

VIR

0.3 to +42

Power Dissipation @ TA

1000

Thermal Resistance,

JunctiontoAmbient

C/W

Operating Junction Temperature

125

Storage Temperature Range

Tstg

55 to +125

Operating Ambient Temperature Range

TL494C
TL494I

0 to +70

25 to +85

Derating Ambient Temperature

NOTE:

1. Maximum thermal limits must be observed.

Motorola, Inc. 1996

Rev 1

TL494

MOTOROLA ANALOG IC DEVICE DATA

RECOMMENDED OPERATING CONDITIONS

Characteristics

Symbol

Min

Typ

Max

Unit

Power Supply Voltage

VCC

7.0

Collector Output Voltage

VC1, VC2

Collector Output Current (Each transistor)

IC1, IC2

200

Amplified Input Voltage

Vin

0.3

VCC 2.0

Current Into Feedback Terminal

lfb

0.3

Reference Output Current

lref

Timing Resistor

1.8

500

Timing Capacitor

0.0047

0.001

Oscillator Frequency

fosc

1.0

200

kHz

ELECTRICAL CHARACTERISTICS

(VCC = 15 V, CT = 0.01

F, RT = 12 k

, unless otherwise noted.)

For typical values TA = 25

C, for min/max values TA is the operating ambient temperature range that applies, unless otherwise noted.

Characteristics

Symbol

Min

Typ

Max

Unit

REFERENCE SECTION

Reference Voltage (IO = 1.0 mA)

Vref

4.75

5.0

5.25

Line Regulation (VCC = 7.0 V to 40 V)

Regline

2.0

Load Regulation (IO = 1.0 mA to 10 mA)

Regload

3.0

Short Circuit Output Current (Vref = 0 V)

ISC

OUTPUT SECTION

Collector OffState Current

(VCC = 40 V, VCE = 40 V)

IC(off)

2.0

100

Emitter OffState Current

VCC = 40 V, VC = 40 V, VE = 0 V)

IE(off)

100

CollectorEmitter Saturation Voltage (Note 2)

CommonEmitter (VE = 0 V, IC = 200 mA)
EmitterFollower (VC = 15 V, IE = 200 mA)

Vsat(C)
Vsat(E)

1.1
1.5

1.3
2.5

Output Control Pin Current

Low State (VOC

0.4 V)

High State (VOC = Vref)

IOCL

IOCH

0.2

3.5

Output Voltage Rise Time

CommonEmitter (See Figure 12)
EmitterFollower (See Figure 13)

100
100

200
200

Output Voltage Fall Time

CommonEmitter (See Figure 12)
EmitterFollower (See Figure 13)

25
40

100
100

NOTE: 2. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient temperature as possible.

TL494

MOTOROLA ANALOG IC DEVICE DATA

ELECTRICAL CHARACTERISTICS

(VCC = 15 V, CT = 0.01

F, RT = 12 k

, unless otherwise noted.)

For typical values TA = 25

C, for min/max values TA is the operating ambient temperature range that applies, unless otherwise noted.

Characteristics

Symbol

Min

Typ

Max

Unit

ERROR AMPLIFIER SECTION

Input Offset Voltage (VO (Pin 3) = 2.5 V)

VIO

2.0

Input Offset Current (VO (Pin 3) = 2.5 V)

IIO

5.0

250

Input Bias Current (VO (Pin 3) = 2.5 V)

IIB

0.1

1.0

Input Common Mode Voltage Range (VCC = 40 V, TA = 25

VICR

0.3 to VCC2.0

Open Loop Voltage Gain (

VO = 3.0 V, VO = 0.5 V to 3.5 V, RL = 2.0 k

)

AVOL

UnityGain Crossover Frequency (VO = 0.5 V to 3.5 V, RL = 2.0 k

)

350

kHz

Phase Margin at UnityGain (VO = 0.5 V to 3.5 V, RL = 2.0 k

)

deg.

Common Mode Rejection Ratio (VCC = 40 V)

CMRR

Power Supply Rejection Ratio (

VCC = 33 V, VO = 2.5 V, RL = 2.0 k

)

PSRR

100

Output Sink Current (VO (Pin 3) = 0.7 V)

0.3

0.7

Output Source Current (VO (Pin 3) = 3.5 V)

IO+

2.0

4.0

PWM COMPARATOR SECTION (Test Circuit Figure 11)

Input Threshold Voltage (Zero Duty Cycle)

VTH

2.5

4.5

Input Sink Current (V(Pin 3) = 0.7 V)

0.3

0.7

DEADTIME CONTROL SECTION (Test Circuit Figure 11)

Input Bias Current (Pin 4) (VPin 4 = 0 V to 5.25 V)

IIB (DT)

2.0

Maximum Duty Cycle, Each Output, PushPull Mode

(VPin 4 = 0 V, CT = 0.01

F, RT = 12 k

)

(VPin 4 = 0 V, CT = 0.001

F, RT = 30 k

)

DCmax

48
45

50
50

Input Threshold Voltage (Pin 4)

(Zero Duty Cycle)
(Maximum Duty Cycle)

Vth

2.8

3.3

OSCILLATOR SECTION

Frequency (CT = 0.001

F, RT = 30 k

)

fosc

kHz

Standard Deviation of Frequency* (CT = 0.001

F, RT = 30 k

)

fosc

3.0

Frequency Change with Voltage (VCC = 7.0 V to 40 V, TA = 25

fosc (

0.1

Frequency Change with Temperature (

TA = Tlow to Thigh)

(CT = 0.01

F, RT = 12 k

)

fosc (

UNDERVOLTAGE LOCKOUT SECTION

TurnOn Threshold (VCC increasing, Iref = 1.0 mA)

Vth

5.5

6.43

7.0

TOTAL DEVICE

Standby Supply Current (Pin 6 at Vref, All other inputs and outputs open)

(VCC = 15 V)
(VCC = 40 V)

ICC

5.5
7.0

10
15

Average Supply Current

(CT = 0.01

F, RT = 12 k

, V(Pin 4) = 2.0 V)

(VCC = 15 V) (See Figure 12)

7.0

* Standard deviation is a measure of the statistical distribution about the mean as derived from the formula,

n = 1

(Xn X)2

N 1

TL494

MOTOROLA ANALOG IC DEVICE DATA

APPLICATIONS INFORMATION

Description

The TL494 is a fixedfrequency pulse width modulation

control circuit, incorporating the primary building blocks
required for the control of a switching power supply. (See
Figure 1.) An internallinear sawtooth oscillator is frequency
programmable by two external components, RT and CT. The
approximate oscillator frequency is determined by:

fosc

1.1

For more information refer to Figure 3.

Output pulse width modulation is accomplished by

comparison of the positive sawtooth waveform across
capacitor CT to either of two control signals. The NOR gates,
which drive output transistors Q1 and Q2, are enabled only
when the flipflop clockinput line is in its low state. This
happens only during that portion of time when the sawtooth
voltage is greater than the control signals. Therefore, an
increase in controlsignal amplitude causes a corresponding
linear decrease of output pulse width. (Refer to the Timing
Diagram shown in Figure 2.)

The control signals are external inputs that can be fed into

the deadtime control, the error amplifier inputs, or the
feedback input. The deadtime control comparator has an
effective 120 mV input offset which limits the minimum output
deadtime to approximately the first 4% of the sawtoothcycle
time. This would result in a maximum duty cycle on a given
output of 96% with the output control grounded, and 48% with
it connected to the reference line. Additional deadtime may
be imposed on the output by setting the deadtimecontrol
input to a fixed voltage, ranging between 0 V to 3.3 V.

Functional Table

Input/Output

Controls

Output Function

fout

fosc

Grounded

Singleended PWM @ Q1 and Q2

1.0

@ Vref

Pushpull Operation

0.5

The pulse width modulator comparator provides a means

for the error amplifiers to adjust the output pulse width from
the maximum percent ontime, established by the deadtime
control input, down to zero, as the voltage at the feedback pin
varies from 0.5 V to 3.5 V. Both error amplifiers have a
common mode input range from 0.3 V to (VCC 2V), and

may be used to sense powersupply output voltage and
current. The erroramplifier outputs are active high and are
ORed together at the noninverting input of the pulsewidth
modulator comparator. With this configuration, the amplifier
that demands minimum output on time, dominates control of
the loop.

When capacitor CT is discharged, a positive pulse is

generated on the output of the deadtime comparator, which
clocks the pulsesteering flipflop and inhibits the output
transistors, Q1 and Q2. With the outputcontrol connected to
the reference line, the pulsesteering flipflop directs the
modulated pulses to each of the two output transistors
alternately for pushpull operation. The output frequency is
equal to half that of the oscillator. Output drive can also be
taken from Q1 or Q2, when singleended operation with a
maximum ontime of less than 50% is required. This is
desirable when the output transformer has a ringback
winding with a catch diode used for snubbing. When higher
outputdrive currents are required for singleended
operation, Q1 and Q2 may be connected in parallel, and the
outputmode pin must be tied to ground to disable the
flipflop. The output frequency will now be equal to that of the
oscillator.

The TL494 has an internal 5.0 V reference capable of

sourcing up to 10 mA of load current for external bias circuits.
The reference has an internal accuracy of

5.0% with a

typical thermal drift of less than 50 mV over an operating
temperature range of 0

to 70

Figure 3. Oscillator Frequency versus

Timing Resistance

500 k

100 k

10 k

1.0 k

500

1.0 k 2.0 k 5.0 k

10 k

20 k

50 k

100 k 200 k

500 k 1.0 M

RT, TIMING RESISTANCE (

)

, OSCILLA

FREQUENCY

(Hz)

f osc

VCC = 15 V

0.01

0.1

CT = 0.001

TL494

MOTOROLA ANALOG IC DEVICE DATA

Figure 4. Open Loop Voltage Gain and

Phase versus Frequency

Figure 5. Percent Deadtime versus

Oscillator Frequency

Figure 6. Percent Duty Cycle versus

Deadtime Control Voltage

1.0

100

1.0 k

10 k

100 k

1.0 M

, OPEN LOOP

VOL

T
AGE GAIN (dB)

VOL

f, FREQUENCY (Hz)

AVOL

20
40

60
80
100

120
140

160
180

, EXCESS PHASE (DEGREES)

VCC = 15 V

VO = 3.0 V

RL = 2.0 k

Figure 7. EmitterFollower Configuration

Output Saturation Voltage versus

Emitter Current

500 k 1.0 k

10 k

100 k

500 k

fosc, OSCILLATOR FREQUENCY (Hz)

, PERCENT

DEADTIME (EACH OUTPUT)

CT = 0.001

0.001

1.0

2.0

3.0

3.5

VDT, DEADTIME CONTROL VOLTAGE (IV)

% DC, PERCENT

DUTY

CYCLE (EACH OUTPUT)

VCC = 15 V

VOC = Vref

1. CT = 0.01

RT = 10 k

2. CT = 0.001

RT = 30 k

Figure 8. CommonEmitter Configuration

Output Saturation Voltage versus

Collector Current

100

200

300

400

IE, EMITTER CURRENT (mA)

, SA

TURA

TION VOL

T
AGE

(V)

CE(sat)

100

200

300

400

IC, COLLECTOR CURRENT (mA)

CE(sat)

, SA

TURA

TION VOL

T
AGE

(V)

Figure 9. Standby Supply Current

versus Supply Voltage

5.0

, SUPPL

CURRENT

(mA)

VCC, SUPPLY VOLTAGE (V)

120
110

100

80
70

60
50
40

30
20

8.0

6.0

4.0

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

9.0

8.0

7.0

6.0

5.0

4.0

3.0

2.0

1.0

TL494

MOTOROLA ANALOG IC DEVICE DATA

Figure 14. ErrorAmplifier Sensing Techniques

Figure 15. Deadtime Control Circuit

Figure 16. SoftStart Circuit

Figure 17. Output Connections for SingleEnded and PushPull Configurations

To Output
Voltage of
System

Vref

Error

Amp

Positive Output Voltage

VO = Vref 1

Vref

Negative Output Voltage

To Output

Voltage of

System

Error

Amp

VO = Vref

R1
R2

Output

Control

Output

Vref

0.001

30k

Max. % on Time, each output

1 +

Output

Vref

Output

Control

SingleEnded

1.0 mA to

500 mA

2.4 V

VOC

Vref

PushPull

1.0 mA to 250 mA

Output

Control

VOC

0.4 V

Figure 18. Slaving Two or More Control Circuits

Figure 19. Operation with Vin > 40 V Using

External Zener

Figure 20. Pulse Width Modulated PushPull Converter

Vref

Master

Vref

Slave
(Additional
Circuits)

Vin > 40V

VZ = 39V

1N975A

VCC

5.0V

Ref

270

Gnd

+Vin = 8.0V to 20V

Comp

OC VREF DT

RT Gnd E1

33k

0.01 0.01

VCC

10k

4.7k

15k

Tip

1N4934

240

35V

4.7k

1.0

+VO = 28 V

IO = 0.2 A

L1 3.5 mH @ 0.3 A

T1 Primary: 20T C.T. #28 AWG

Secondary: 12OT C.T. #36 AWG

Core: Ferroxcube 1408PL003CB

All capacitors in

TL494

0.001

35V

25V

Tip

TL494

MOTOROLA ANALOG IC DEVICE DATA

Test

Conditions

Results

Line Regulation

Vin = 10 V to 40 V

14 mV 0.28%

Load Regulation

Vin = 28 V, IO = 1.0 mA to 1.0 A

3.0 mV 0.06%

Output Ripple

Vin = 28 V, IO = 1.0 A

65 mV pp P.A.R.D.

Short Circuit Current

Vin = 28 V, RL = 0.1

1.6 A

Efficiency

Vin = 28 V, IO = 1.0 A

71%

TL494

MOTOROLA ANALOG IC DEVICE DATA

OUTLINE DIMENSIONS

N SUFFIX

PLASTIC PACKAGE

CASE 64808

ISSUE 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

16 PL

SEATING

PLANE

T

0.25 (0.010)

DIM

MIN

MAX

MIN

MAX

MILLIMETERS

INCHES

0.740

0.770

18.80

19.55

0.250

0.270

6.35

6.85

0.145

0.175

3.69

4.44

0.015

0.021

0.39

0.53

0.040

0.70

1.02

1.77

0.100 BSC

2.54 BSC

0.050 BSC

1.27 BSC

0.008

0.015

0.21

0.38

0.110

0.130

2.80

3.30

0.295

0.305

7.50

7.74

0.020

0.040

0.51

1.01

D SUFFIX

PLASTIC PACKAGE

CASE 751B05

(SO16)
ISSUE J

NOTES:

1. DIMENSIONING AND TOLERANCING PER

ANSI Y14.5M, 1982.

2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS A AND B DO NOT INCLUDE

MOLD PROTRUSION.

4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)

PER SIDE.

5. DIMENSION D DOES NOT INCLUDE DAMBAR

PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 (0.005) TOTAL
IN EXCESS OF THE D DIMENSION AT
MAXIMUM MATERIAL CONDITION.

SEATING

PLANE

X 45

8 PL

B

A

0.25 (0.010)

T

16 PL

0.25 (0.010)

DIM

MIN

MAX

MIN

MAX

INCHES

MILLIMETERS

9.80

10.00

0.386

0.393

3.80

4.00

0.150

0.157

1.35

1.75

0.054

0.068

0.35

0.49

0.014

0.019

0.40

1.25

0.016

0.049

1.27 BSC

0.050 BSC

0.19

0.25

0.008

0.009

0.10

0.25

0.004

0.009

5.80

6.20

0.229

0.244

0.25

0.50

0.010

0.019

TL494

MOTOROLA ANALOG IC DEVICE DATA

Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding
the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and
specifically disclaims any and all liability, including without limitation consequential or incidental damages. "Typical" parameters which may be provided in Motorola
data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals"
must be validated for each customer application by customer's technical experts. Motorola does not convey any license under its patent rights nor the rights of
others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other
applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury
or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola
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 death associated with such unintended or unauthorized use, even if such claim alleges that Motorola
was negligent regarding the design or manufacture of the part. Motorola and are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal
Opportunity/Affirmative Action Employer.

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TL494/D

*TL494/D*

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