GL494

1

GL494

PWM CONTROL CIRCUIT

Description

The GL494 incorporates on a single monolithic chip all the

functions required in the construction of a pulse-width-

modulation control circuit. Designed primarily for power

supply control, the GL494 contains an on-chip 5-volt

regulator, two error amplifiers, adjustable oscillator, dead-

time control comparator, pulse-steering flip-flop, and

output-control

circuitry.

The

uncommitted

output

transistors pro-vide either common-emitter or emitter-

follower output capability. Push-pull or single-ended

output operation may be selected through the output-

control function. The ar-chitecture of the GL494 prohibits

the possibility of either output being pulsed twice during

push-pull operation.

Features

— Complete PWM Power Control Circuitry

— Uncommitted Outputs for 200mA Sink or Source

— Output Control Selects Single-Ended or Push-Pull

Operation

— Internal Circuitry Prohibits Double Pulse at Either

Output

— Internal Regulator Provides a Stable 5V Reference

Supply

— Variable Dead-Time Provides Control Over Total

Range

Pin Configuration

Function Table

Output Control

Output Function

Grounded

Single-ended or Parallel Output

At

ref

V

Normal Push-Pull Operation

Block Diagram

OSCILLATOR

REFERENCE

REGULATOR

NONINV INPUT

INV. INPUT

FEEDBACK

DEAD TIME CONTROL

Cr

Rr

GND

C1

NON INV INPUT

INV. INPUT

REF. OUT

OUTPUT CONTROL

Vcc

C2

E2

E1

DEAD

TIME

CONTROL

NONINVERTING(1)

INPUT

INVERTING

(2)

INPUT

NONINVERTING(16)

INPUT

INVERTING

(15)

INPUT

FEEDBACK

ERROR

AMPLIFIERS

PWM

COMPARATOR

OUTPUT

CONTROL

(See Function Table)

PULSE STEERING

FLIP FLOP

REF OUT

GND

E1(9) C1(8)

E1(10) C2(11)

(4)

(3)

(7)

(12)

(14)

(13)

T

Q

Q

0.1V

+

+

−

−

ERROR AMP1

ERROR AMP2

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9