TEXAS INSTRUMENTS UC1827-1, UC1827-2, UC2827-1, UC2827-2, UC3827-1, UC3827-2 Data Sheet manual guide

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UC1827-1, UC1827-2

UC2827-1, UC2827-2

UC3827-1, UC3827-2

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SLUS365A–APRIL 1999–REVISED AUGUST

BUCK CURRENT/VOLTAGE FED PUSH-PULL

PWM CONTROLLERS

FEATURES DESCRIPTION

Ideal for Multiple Output and/or High

The UC3827 family of controller devices provides an

Voltage Output Voltage Converters integrated control solution for cascaded buck and

Up to k Hz Operation push-pull converters. These converters are known as•

current fed or voltage fed push-pull converters and•

High Voltage, High Current Floating

are ideally suited for multiple output and/or high

Driver for Buck Converter Stage

voltage output applications. In both current fed and

UC3827-1 Current Fed Controller has voltage fed modes, the push-pull switches are driven

Push-Pull Drivers with Overlapping at 50% nominal duty cycles and at one half the

Periods switching frequency of the buck stage. In the current Conduction

fed mode, the two switches are driven with speci-•

UC3827-2 Voltage Fed Controller has

fied over-lap period to prevent ringing and voltage Push-Pull

Drivers with Nonoverlapping

stress on the devices. In the voltage fed mode, the

Conduction Periods

two switches are driven with specified gap time

Average Current Mode, Peak Current between the switches to prevent shorting the trans-

Mode or Voltage Mode with Input former across the energy storage capacitor and to

Feedforward Control for Buck prohibit excessive currents flowing through the de-Voltage

Stage vices.Power

Wide Bandwidth, Low Offset, The converter's output voltage is regulated by pulse

Differential Current Sense Amplifier width modulation of the buck switch. The UC3827

contains complete protection and PWM control func-•

Precise Short Circuit Current Control

tions for the buck converter. Easy control of the

floating switch is accomplished by the floating drive

circuitry. The gate drive waveform is level shifted to

support an input voltage up to VDC.

BLOCK DIAGRAM

CEAOVEAO RAMPCEA+

Voltage Error Amplifier

PWM Comparator0.7 V

Current Error

Amplifier

CSAO Flying

+3 V Driver

CSA+ QS

ILIM Comparator BUCK

CSA− Current Sense

Amplifier

SS OSC

INHBT

SYNC PGND

CT DELAY

500 k Hz

Push/Pull

RT MAX

Drivers

VCC REF

UVLO UVLO DELAY PULL

DELAY

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas

Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date. Copyright 1999–2005, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.