Advanced Regulating Pulse Width Modulators

FEATURES

•

Dual Uncommitted 40V, 200mA

Output Transistors

•

1% Accurate 5V Reference

•

Dual Error Amplifiers

•

Wide Range, Variable Deadtime

•

Single-ended or Push-pull

Operation

•

Under-voltage Lockout With

Hysteresis

•

Double Pulse Protection

•

Master or Slave Oscillator

Operation

•

UC495A: Internal 39V Zener Diode

•

UC495A: Buffered Steering Control

DESCRIPTION

This entire series of PWM modulators each provide a complete pulse width

modulation system in a single monolithic integrated circuit. These devices in-

clude a 5V reference accurate to

±1%, two independent amplifiers usable for

both voltage and current sensing, an externally synchronizable oscillator

with its linear ramp generator, and two uncommitted transistor output

switches. These two outputs may be operated either in parallel for single-

ended operation or alternating for push-pull applications with an externally

controlled dead-band. These units are internally protected against double-

pulsing of a single output or from extraneous output signals when the input

supply voltage is below minimum.

The UC495A contains an on-chip 39V zener diode for high-voltage applica-

control that overrides the internal control of the pulse steering flip-flop.

The UC494A is packaged in a 16-pin DIP, while the UC495A is packaged in

an 18 pin DIP. The UC494A, UC495A are specified for operation over the full

military temperature range of -55°C to +125°C, while the UC494AC,

UC495AC are designed for industrial applications from 0°C to +70°C.

BLOCK DIAGRAM

UC494A/AC

UC495A/AC

10/93