Press Center
Home About us Products Support Quality & Certification Career Contact us
• Power Management
    Linear Regulators
    Low Dropout Linear Regulators
    DDR Termination Regulators
    Shunt Reference Regulators
    Step Down Switching Regulators
    Switching Regulator
    Step-Up DC-DC Converter
    PWM Controller
    White LED Driver
    Supervisory Circuit
    Voltage Detection and System R
    USB Power Switch
    Power Factor Control
    Li-Battery Protection or Charg
    FET Bias Controllers
    Combo IC
    Inverting DC-DC Converter
• Amplifier / Comparator
    Audio Amplifiers
    Operational Amplifier
    Voltage Comparator
• Analog Switches
    Video Signal Switch
    Analog Multiplexers, Demultipl
• Hall ICs
• Special Application ICs
    Motor Controller IC
    Interface and Driver Circuit
    Telecommunication Circuit
    Melody IC
    Alarm /Sound Generator IC
    Remote Controller IC
    Television Circuit
    Leakage Current Detector
    Automotive IC
    A-D or D-A Converters
    Radio and Cassette Recorder Ci
    Mouse&Keyboard Controller
    Transient Voltage Suppressors
    Sense Monitor
    Video Filter
    ZCB snubber
• Logic
    Power Mosfet
• SCRs
Home > Step Down Switching Regulators
UC3854 Datasheet





The UTC UC3854 provide all the functions necessary for active

power factor corrected preregulators. The controller achieves near

unity power factor by shaping the AC input line current waveform to

correspond to that of AC input line voltage. Average current mode

control maintains stable, low distortion sinusoidal line current

without the need for slope compensation, unlike peak current mode


Designed in UTC’s Bipolar process, the UTC UC3854 offers

new features such as wide bandwidth, low offset Current Amplifier,

a faster responding and improved accuracy enable comparator, a

VREF "good" comparator, UVLO threshold options (16/10V for

offline, 10.5/10V for startup from an auxiliary 12V regulator), lower

startup supply current, and an enhanced multiply/divide circuit.

New features like the improved amplifier current sinking capability,

amplifier output clamps, and low offset VAC pin reduce the external

component count while improving performance. Improved common

mode input range of the Multiplier output/Current Amp input allow

the designer greater flexibility in choosing a method for current

sensing. Unlike its predecessor, the maximum multiplier output

current is now clamped to a maximum of 2 * IAC at all times.

A 1% 7.5V reference, fixed frequency oscillator, PWM, Voltage

Amplifier with softstart, line voltage feedforward (VRMS squarer),

input supply voltage clamp, and over current comparator round out

the list of features.


* Controls Boost Preregulator to Near Unity Power Factor

* Limits Line Distortion

* World-Wide Line Operation

* Accurate Power Limiting

* Fixed Frequency Average Current Mode Control

* High Bandwidth (5MHz), Low Offset Current Amplifier

* Integrated Current and Voltage Amp Output Clamps

* Multiplier Improvements: Linearity, 500mV VAC Offset (eliminates external resistor), 0-5V Multout Common Mode Range

* VREF "GOOD" Comparator

* Faster and Improved Accuracy ENABLE Comparator

* 300uA Startup Supply Current

About us  |  Products  |  Contact us
Copyright 2011 UTC All received