PULSE-WIDTH-MODULATION CONTROL CIRCUITS
AZ494
Rev.1.0
1
March. 2003
Advanced Analog Circuits
Data Sheet
General Description
The AZ494 incorporates on a single chip all the func-
tions required in the construction of a pulse-width-
modulation (PWM) control circuit. Designed primarily
for power supply control, this device offers the flexibil-
ity to tailor the power supply control circuitry to a spe-
cific application.
The AZ494 contains two error amplifiers, an on-chip
adjustable oscillator, a dead-time control (DTC) com-
parator, a pulse-steering control flip-flop, a 5V regula-
tor, and output control circuits. The error amplifiers
exhibit a common-mode voltage range from -0.3V to
VCC-2V. The dead-time control comparator has a fixed
offset that provides approximately 5% dead time. The
on-chip oscillator can be bypassed by terminating the
RT pin to the reference output and providing a saw-
tooth input to the CT pin, or it can drive the common
circuits in synchronous multiple-rail power supplies.
The uncommitted output transistors can be configured
in either common-emitter or emitter-follower output
topology. The AZ494 provides for push-pull or single-
ended output operation, which can be selected through
the output control function. The architecture of this
device prohibits the possibility of either output being
pulsed twice during push-pull operation. The AZ494 is
characterized for operation from -40oC to 85oC.
Features
·
Complete PWM power-control circuitry
·
Uncommitted outputs for 200mA 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 5V reference
supply with 5% tolerance
·
Circuit architecture allows easy synchronization
Applications
·
SMPS
·
Back Light Inverter
SOIC-16
DIP-16
Figure 1. Package Types of AZ494
