LM5025B

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SNVS354B – JULY 2005 – REVISED MARCH 2013

LM5025B Active Clamp Voltage Mode PWM Controller

Check for Samples: LM5025B

1

FEATURES

DESCRIPTION

The LM5025B is a functional variant of the LM5025

2

•

Internal Start-Up Bias Regulator

active

clamp

PWM

controller.

The

functional

•

3A Compound Main Gate Driver

differences of the LM5025B are as follows:

•

Programmable Line Under-Voltage Lockout

•

The maximum PWM duty cycle is limited to less

(UVLO) with Adjustable Hysteresis

than 75% to reduce voltage stress on the power

MOSFETs.

•

Voltage Mode Control with Feed-Forward

•

The CS2 hiccup mode threshold is increased to

•

Adjustable Dual Mode Over-Current Protection

0.5V

•

Programmable Overlap or Deadtime between

•

The CS2 filter discharge device is disabled

the Main and Active Clamp Outputs

•

The VCC regulator continues to operate when the

•

Volt x Second Maximum Duty Cycle Clamp

line UVLO is below the threshold of normal

•

Programmable Soft-Start

operation

•

Current Sense Leading Edge Blanking

•

The VREF regulator is switched off when the line

UVLO input falls below the operating threshold

•

Single Resistor Programmable Oscillator

•

The internal 5k

Ω COMP pin pull-up resistor is

•

Oscillator Up / Down Sync Capability

removed

•

Precision 5V Reference

The LM5025B PWM controller contains all of the

•

Thermal Shutdown

features necessary to implement power converters

utilizing the Active Clamp / Reset technique. With the

PACKAGES

active

clamp

technique,

higher

efficiencies

and

•

TSSOP-16

greater power densities can be realized compared to

conventional catch winding or RDC clamp / reset

•

WSON-16 (5x5 mm) Thermally Enhanced

techniques. Two control outputs are provided, the

main power switch control (OUT_A) and the active

clamp switch control (OUT_B). The two internal

compound gate drivers parallel both MOS and Bipolar

devices, providing superior gate drive characteristics.

This controller is designed for high-speed operation

including an oscillator frequency range up to 1MHz

and total PWM and current sense propagation delays

less than 100ns.

The

LM5025B

includes

a

high-voltage

start-up

regulator that operates over a wide input range of

13V to 100V. Additional features include: Line Under

Voltage

Lockout

(UVLO),

softstart,

oscillator

UP/DOWN sync capability, precision reference and

thermal shutdown.

1

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2

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PRODUCTION DATA information is current as of publication date.

Copyright © 2005–2013, 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.