HTC TL494 Service Manual

现货库存、技术资料、百科信息、热点资讯，精彩尽在鼎好!

p

Pulse-Width-Modulation Control Circuits TL494

CT

RT

GND

C1

SOP16/DIP16

(TOP VIEW)

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

NONINV
INPUT

INV INPUT

REF OUT

OUTPUT
CONTROL

Vcc

C2

E2

E1

9

Error
AMP 2

FEATURES

● Complete PWM Power Control Circuitry

● Uncommitted Outputs for 200 Ma Sink or Source Current

● Output Control Selects Single-Ended or Push-Pull Operation

● Internal Circuitry Prohibits Double Pulse at Either Output

● Variable Dead-Time Provides Control over Total Range

● Internal Regulator Provides a Stable 5-V Reference Supply,5%

● Circuit Architecture Allows Easy Synchronization

Error
AMP 1

NONINV
INPUT

INV INPUT

FEEDBACK

DEAD-TIME
CONTROL

DESCRIPTION

The TL494 incorporate on a single monolithic chip all the functions
required in the construction of a pulse-width-modulation control,
these devices offer the systems engineer the flexibility to tailor
the power supply control circuitry to his application.
The TL494 contains an error amplifier, an on-chip adjustable
oscillator, a dead-time control comparator, pulse-steering control

ORDERING INFORMATION

Device Package
TL494D 16 SOP
TL494N 18 DIP

flip-flop, a 5-volt, 5% precision regulator, and output-control circuit.
The error amplifier exhibits a common-mode voltage range from -0.3 volts to Vcc -2 volts. The dead-time control
comparator has a fixed offset that provides approximately 5% dead time when externally altered. The on-chip

oscillator may be bypassed by terminating R

(pin 6) to the reference output and providing a sawtooth in put to

T

CT (pin 5), or it may be used to drive the common circuits in synchronous multiple-rail power supplies. The
uncommited output transistors provide either common-emitter or emitter-follower output capability. Each Device

rovides for push-pull or single-ended output operation, which may be selected through the output-control funct

-ion. The architecture of these devices prohibits the possibility of either output being pulsed twice during push

-pull operation.

Functional Block Diagram

R
C

DEAD

TIME

CONTROL

NONINVERTING INPUT

INVERTING INPUT

NONINVERTING INPUT

INVERTING INPUT

Mar. 2006-Rev06

T

T

0.1V

ERROR AMPLIFIER

ERROR AMPLIFIER

OSCILLATOR

DEAD-TIME CONTROL COMPARATOR

+

1

-

+

2

-

PWM COMPARATOR

FEEDBACK

145

OUTPUT CONTROL

C1

PULSE-STEERING FLIP-FLOP

REFERENCE

Q1

Q2

C1

E1

C2

E2

Vcc

Vref

GND

HTC

Pulse-Width-Modulation Control Circuits TL494

Parameter measurement information

Vcc = 15V

VOLTAGE

AT C1

TEST
INPUTS

50KΩ

12KΩ

0.01uF

DEAD-TIME

FEEDBACK

R

T

C

T

(+)

(-)

(+)

(-)

OUTPUT
CONTROL

ERROR

Vcc

GND

TEST CIRCUIT

C1

E1

C2

E2

REF OUT

150 Ω
2W

150 Ω
2W

OUTPUT 1

OUTPUT 2

Vcc

VOLTAGE

AT C2

VOLTAGE

AT C

DEAD-TIME

CONTROL

INPUT

FEEDBACK

DUTY

CIRCLE

Mar. 2006-Rev06

0

Vcc

0

T

THRESHOLD VOLTAGE

0 V

THRESHOLD VOLTAGE

0.7 V

0% MAX

0%

Figure 1. OPERATIONAL TEST CIRCUIT AND WAVEFORMS

HTC

146