Semiconductor Components Industries, LLC, 2004

April, 2004 - Rev. 5

Publication Order Number:

TL494/D

TL494, NCV494
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

On-Chip Oscillator with Master or Slave Operation

On-Chip Error Amplifiers

On-Chip 5.0 V Reference

Adjustable Deadtime Control

Uncommitted Output Transistors Rated to 500 mA Source or Sink

Output Control for Push-Pull or Single-Ended Operation

Undervoltage Lockout

NCV Prefix for Automotive and Other Applications Requiring Site

and Control Changes

MAXIMUM RATINGS

(Full operating ambient temperature range applies,

unless otherwise noted.)

Rating

Symbol

Value

Unit

Power Supply Voltage

Collector Output Voltage

Collector Output Current

(Each transistor) (Note 1)

, I

500

Amplifier Input Voltage Range

-0.3 to +42

Power Dissipation @ T

1000

Thermal Resistance, Junction-to-Ambient

C/W

Operating Junction Temperature

125

Storage Temperature Range

stg

-55 to +125

Operating Ambient Temperature Range

TL494B
TL494C
TL494I
NCV494B

-40 to +125

0 to +70

- 40 to +85

-40 to +125

Derating Ambient Temperature

1. Maximum thermal limits must be observed.

PIN CONNECTIONS

Ground

Inv

Input

0.1 V

Oscillator

5.0 V

REF

(Top View)

Noninv
Input

Inv
Input

ref

Output
Contro
l

Noninv

Input

Compen/PWN

Comp Input

Deadtime

Control

Error

Amp

Error

Amp

Device

Package

Shipping

ORDERING INFORMATION

TL494CD

SO-16

48 Units/Rail

SO-16

D SUFFIX

CASE 751B

TL494xD

AWLYWW

MARKING

DIAGRAMS

= B, C or I

= Assembly Location

WL, L

= Wafer Lot

YY, Y

= Year

WW, W = Work Week

PDIP-16

N SUFFIX

CASE 648

TL494xN

AWLYYWW

TL494CDR2

2500 Tape & Reel

SO-16

TL494CN

25 Units/Rail

PDIP-16

TL494IN

25 Units/Rail

PDIP-16

SO-16

TL494BD

48 Units/Rail

TL494BDR2

2500 Tape & Reel

SO-16

http://onsemi.com

*This marking diagram also applies to NCV494.

NCV494BDR2*

2500 Tape & Reel

SO-16

For information on tape and reel specifications,

including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specification
Brochure, BRD8011/D.

*NCV494: T

low

= -40

C, T

high

= +125

Guaranteed by design. NCV prefix is for
automotive and other applications requiring site
and change control.

TL494, NCV494

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RECOMMENDED OPERATING CONDITIONS

Characteristics

Symbol

Min

Typ

Max

Unit

Power Supply Voltage

7.0

Collector Output Voltage

, V

Collector Output Current (Each transistor)

, I

200

Amplified Input Voltage

-0.3

- 2.0

Current Into Feedback Terminal

0.3

Reference Output Current

ref

Timing Resistor

1.8

500

Timing Capacitor

0.0047

0.001

Oscillator Frequency

osc

1.0

200

kHz

ELECTRICAL CHARACTERISTICS

= 15 V, C

= 0.01

F, R

= 12 k

, unless otherwise noted.)

For typical values T

= 25

C, for min/max values T

is the operating ambient temperature range that applies, unless otherwise noted.

Characteristics

Symbol

Min

Typ

Max

Unit

REFERENCE SECTION

Reference Voltage (I

= 1.0 mA)

ref

4.75

5.0

5.25

Line Regulation (V

= 7.0 V to 40 V)

Reg

line

2.0

Load Regulation (I

= 1.0 mA to 10 mA)

Reg

load

3.0

Short Circuit Output Current (V

ref

= 0 V)

OUTPUT SECTION

Collector Off-State Current

= 40 V, V

= 40 V)

C(off)

2.0

100

Emitter Off-State Current

= 40 V, V

= 0 V)

E(off)

-100

Collector-Emitter Saturation Voltage (Note 2)

Common-Emitter (V

= 0 V, I

= 200 mA)

Emitter-Follower (V

= 15 V, I

= -200 mA)

sat(C)

sat(E)

-
-

1.1
1.5

1.3
2.5

Output Control Pin Current

Low State (V

0.4 V)

High State (V

= V

ref

)

OCL

OCH

-
-

0.2

3.5

Output Voltage Rise Time

Common-Emitter (See Figure 12)
Emitter-Follower (See Figure 13)

-
-

100
100

200
200

Output Voltage Fall Time

Common-Emitter (See Figure 12)
Emitter-Follower (See Figure 13)

-
-

25
40

100
100

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

TL494, NCV494

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ELECTRICAL CHARACTERISTICS

= 15 V, C

= 0.01

F, R

= 12 k

, unless otherwise noted.)

For typical values T

= 25

C, for min/max values T

is the operating ambient temperature range that applies, unless otherwise noted.

Characteristics

Symbol

Min

Typ

Max

Unit

ERROR AMPLIFIER SECTION

Input Offset Voltage (V

O (Pin 3)

= 2.5 V)

2.0

Input Offset Current (V

O (Pin 3)

= 2.5 V)

5.0

250

Input Bias Current (V

O (Pin 3)

= 2.5 V)

-0.1

-1.0

Input Common Mode Voltage Range (V

= 40 V, T

= 25

ICR

-0.3 to V

-2.0

Open Loop Voltage Gain (

= 3.0 V, V

= 0.5 V to 3.5 V, R

= 2.0 k

)

VOL

Unity-Gain Crossover Frequency (V

= 0.5 V to 3.5 V, R

= 2.0 k

)

C-

350

kHz

Phase Margin at Unity-Gain (V

= 0.5 V to 3.5 V, R

= 2.0 k

)

deg.

Common Mode Rejection Ratio (V

= 40 V)

CMRR

Power Supply Rejection Ratio (

= 33 V, V

= 2.5 V, R

= 2.0 k

)

PSRR

100

Output Sink Current (V

O (Pin 3)

= 0.7 V)

O-

0.3

0.7

Output Source Current (V

O (Pin 3)

= 3.5 V)

2.0

-4.0

PWM COMPARATOR SECTION (Test Circuit Figure 11)

Input Threshold Voltage (Zero Duty Cycle)

2.5

4.5

Input Sink Current (V

(Pin 3)

= 0.7 V)

I-

0.3

0.7

DEADTIME CONTROL SECTION (Test Circuit Figure 11)

Input Bias Current (Pin 4) (V

Pin 4

= 0 V to 5.25 V)

IB (DT)

-2.0

-10

Maximum Duty Cycle, Each Output, Push-Pull Mode

Pin 4

= 0 V, C

= 0.01

F, R

= 12 k

)

Pin 4

= 0 V, C

= 0.001

F, R

= 30 k

)

max

48
45

50
50

Input Threshold Voltage (Pin 4)

(Zero Duty Cycle)
(Maximum Duty Cycle)

-
0

2.8

3.3

OSCILLATOR SECTION

Frequency (C

= 0.001

F, R

= 30 k

)

osc

kHz

Standard Deviation of Frequency* (C

= 0.001

F, R

= 30 k

)

osc

3.0

Frequency Change with Voltage (V

= 7.0 V to 40 V, T

= 25

osc

(

0.1

Frequency Change with Temperature (

= T

low

to T

high

)

= 0.01

F, R

= 12 k

)

osc

(

UNDERVOLTAGE LOCKOUT SECTION

Turn-On Threshold (V

increasing, I

ref

= 1.0 mA)

5.5

6.43

7.0

TOTAL DEVICE

Standby Supply Current (Pin 6 at V

ref

, All other inputs and outputs open)

= 15 V)

= 40 V)

-
-

5.5
7.0

10
15

Average Supply Current

= 0.01

F, R

= 12 k

, V

(Pin 4)

= 2.0 V)

= 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

- X)

N - 1

TL494, NCV494

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APPLICATIONS INFORMATION

Description

The TL494 is a fixed-frequency pulse width modulation

control circuit, incorporating the primary building blocks
required for the control of a switching power supply. (See
Figure 1.) An internal-linear sawtooth oscillator is
frequency- programmable by two external components, R

and C

. The approximate oscillator frequency is determined

by:

osc

1.1

For more information refer to Figure 3.

Output pulse width modulation is accomplished by

comparison of the positive sawtooth waveform across
capacitor C

to either of two control signals. The NOR gates,

which drive output transistors Q1 and Q2, are enabled only
when the flip-flop clock-input 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 control-signal 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
sawtooth-cycle 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 deadtime-control input to a fixed voltage,
ranging between 0 V to 3.3 V.

Functional Table

Input/Output

Controls

Output Function

out

osc

Grounded

Single-ended PWM @ Q1 and Q2

1.0

@ V

ref

Push-pull 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 on-time, 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 (V

- 2V), and

may be used to sense power-supply output voltage and
current. The error-amplifier outputs are active high and are
ORed together at the noninverting input of the pulse-width
modulator comparator. With this configuration, the
amplifier

that demands minimum output on time, dominates

control of the loop.

When capacitor C

is discharged, a positive pulse is

generated on the output of the deadtime comparator, which
clocks the pulse-steering flip-flop and inhibits the output
transistors, Q1 and Q2. With the output-control connected
to the reference line, the pulse-steering flip-flop directs the
modulated pulses to each of the two output transistors
alternately for push-pull operation. The output frequency is
equal to half that of the oscillator. Output drive can also be
taken from Q1 or Q2, when single-ended operation with a
maximum on-time 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
output-drive currents are required for single-ended
operation, Q1 and Q2 may be connected in parallel, and the
output-mode pin must be tied to ground to disable the
flip-flop. 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

TIMING RESISTANCE (

, OSCILLA

OR FREQUENCY

(Hz)

f osc

= 15 V

0.01

0.1

= 0.001

TL494, NCV494

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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)

VOL

20
40

60
80
100

120
140

160
180

, EXCESS PHASE (DEGREES)

= 15 V

= 3.0 V

= 2.0 k

Figure 7. Emitter-Follower Configuration

Output Saturation Voltage versus

Emitter Current

500 k 1.0 k

10 k

100 k

500 k

osc

, OSCILLATOR FREQUENCY (Hz)

% DT

, PERCENT

DEADTIME (EACH OUTPUT)

= 0.001

0.001

1.0

2.0

3.0

3.5

, DEADTIME CONTROL VOLTAGE (IV)

% DC, PERCENT

DUTY

CYCLE (EACH OUTPUT)

= 15 V

= V

ref

1. C

= 0.01

= 10 k

2. C

= 0.001

= 30 k

Figure 8. Common-Emitter Configuration

Output Saturation Voltage versus

Collector Current

100

200

300

400

EMITTER CURRENT (mA)

, SA

TURA

TION VOL

T
AGE (V)

CE(sat)

100

200

300

400

, 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)

, 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, NCV494

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Figure 10. Error-Amplifier Characteristics

Figure 11. Deadtime and Feedback Control Circuit

Figure 12. Common-Emitter Configuration

Test Circuit and Waveform

Error Amplifier

Under Test

Feedback

Terminal

(Pin 3)

Other Error

Amplifier

ref

= 15V

150

Output 1

Output 2

C1
E1

Ref
Out

Gnd

Output
Control

(+)

(+)
(-)

(-)

Feedback

Deadtime

Error

Test

Inputs

50k

150

Figure 13. Emitter-Follower Configuration

Test Circuit and Waveform

15pF

Each
Output
Transistor

15V

90%

10%

90%

10%

15pF

Each
Output
Transistor

15V

90%

10%

90%

10%

Gnd

TL494, NCV494

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Figure 14. Error-Amplifier Sensing Techniques

Figure 15. Deadtime Control Circuit

Figure 16. Soft-Start Circuit

Figure 17. Output Connections for Single-Ended and Push-Pull Configurations

To Output
Voltage of
System

ref

Error

Amp

Positive Output Voltage

= V

ref

1 +

ref

Negative Output Voltage

To Output

Voltage of

System

Error

Amp

= V

ref

R1
R2

Output

Control

Output

ref

0.001

30k

Max. % on Time, each output

45 -

1 +

Output

ref

Output

Control

Single-Ended

1.0 mA to

500 mA

2.4 V

ref

Push-Pull

1.0 mA to
250 mA

Output

Control

0.4 V

1.0 mA to
250 mA

L1 - 3.5 mH @ 0.3 A

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

T1 -

Secondary: 12OT C.T. #36 AWG

T1 -

Core: Ferroxcube 1408P-L00-3CB

TL494, NCV494

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Figure 18. Slaving Two or More Control Circuits

Figure 19. Operation with V

> 40 V Using

External Zener

Figure 20. Pulse Width Modulated Push-Pull Converter

ref

Master

ref

Slave
(Additional
Circuits)

> 40V

= 39V

1N975A

5.0V

Ref

270

Gnd

= 8.0V to 20V

Comp

REF

Gnd

33k

0.01 0.01

10k

4.7k

15k

Tip

1N4934

240

35V

4.7k

1.0

= 28 V

= 0.2 A

All capacitors in

TL494

0.001

35V

25V

Tip

Test

Conditions

Results

Line Regulation

= 10 V to 40 V

14 mV 0.28%

Load Regulation

= 28 V, I

= 1.0 mA to 1.0 A

3.0 mV 0.06%

Output Ripple

= 28 V, I

= 1.0 A

65 mV pp P.A.R.D.

Short Circuit Current

= 28 V, R

= 0.1

1.6 A

Efficiency

= 28 V, I

= 1.0 A

71%

TL494, NCV494

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PACKAGE DIMENSIONS

PDIP-16

N SUFFIX

CASE 648-08

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

SO-16

D SUFFIX

CASE 751B-05

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, NCV494

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ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to 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 liability
arising 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. All
operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights
nor 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 applications
intended 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. Should
Buyer 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 death
associated 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 Equal
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PUBLICATION ORDERING INFORMATION

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USA/Canada

Japan: ON Semiconductor, Japan Customer Focus Center

2-9-1 Kamimeguro, Meguro-ku, Tokyo, Japan 153-0051
Phone: 81-3-5773-3850

TL494/D

SWITCHMODE is a trademark of Semiconductor Components Industries, LLC.

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