1/97

•

Automatic Feed Forward Compensation

•

Programmable Pulse-by-Pulse Current

Limiting

•

Automatic Symmetry Correction in Push-pull

Configuration

•

Enhanced Load Response Characteristics

•

Parallel Operation Capability for Modular

Power Systems

•

Differential Current Sense Amplifier with

Wide Common Mode Range

•

Double Pulse Suppression

•

500mA (Peak) Totem-pole Outputs

•±1% Bandgap Reference

•

Under-voltage Lockout

•

Soft Start Capability

•

Shutdown Terminal

•

500kHZ Operation

Current Mode PWM Controller

The UC1846/7 family of control ICs provides all of the necessary

features to implement fixed frequency, current mode control

schemes while maintaining a minimum external parts count. The su-

perior performance of this technique can be measured in improved

line regulation, enhanced load response characteristics, and a sim-

pler, easier-to-design control loop. Topological advantages include

inherent pulse-by-pulse current limiting capability, automatic sym-

metry correction for push-pull converters, and the ability to parallel

“power modules" while maintaining equal current sharing.

Protection circuitry includes built-in under-voltage lockout and pro-

grammable current limit in addition to soft start capability. A shut-

down function is also available which can initiate either a complete

shutdown with automatic restart or latch the supply off.

Other features include fully latched operation, double pulse sup-

pression, deadline adjust capability, and a

±1% trimmed bandgap

reference.

The UC1846 features low outputs in the OFF state, while the

UC1847 features high outputs in the OFF state.

UC1846/7

UC2846/7

UC3846/7

BLOCK DIAGRAM

FEATURES

DESCRIPTION