LM5027A

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SNVS642B – APRIL 2010 – REVISED MARCH 2013

Voltage Mode Active Clamp Controller

Check for Samples: LM5027A

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FEATURES

DESCRIPTION

The LM5027A is a functional variant of the LM5027

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•

Voltage-Mode Control

active

clamp

PWM

controller.

The

functional

•

Line Feed-Forward PWM Ramp

difference of the LM5027A is that the maximum duty

•

Internal 105V Rated Start-Up Bias Regulator

cycle of the LM5027A is decreased from 91% to 71%.

In addition, the oscillator timing equation has been

•

Programmable Line Under-Voltage Lockout

modified.

(UVLO) with Adjustable Hysteresis

The

LM5027A

pulse-width

modulation

(PWM)

•

Versatile Dual Mode Over-Current Protection

controller contains all of the features necessary to

•

Programmable Volt-Second Limiter and Soft-

implement power converters utilizing the Active

Start

Clamp / Reset technique. With the active clamp

•

Programmable Synchronous Rectifier Soft-

technique, higher efficiencies and greater power

Start and Stop

densities can be realized compared to conventional

catch winding or RDC clamp / reset techniques.

•

Precise 500mV Over-Current Comparator

Three control outputs are provided: the main power

•

Current Sense Leading Edge Blanking

switch control (OUTA), the active clamp switch

•

Programmable Oscillator With 1 MHz

control (OUTB), and secondary side synchronous

Maximum Frequency and Synchronization

rectifier control (OUTSR). The timing between the

Capability

control outputs is adjustable with external resistors

that program internal precision timers. This controller

•

Precision 5V Reference

is designed for high-speed operation including an

•

Programmable Time Delays Between Outputs

oscillator frequency range up to 1 MHz and total

•

A 70% Maximum Duty Cycle

PWM propagation delays less than 50 ns. The

LM5027A includes a high-voltage startup regulator

with a maximum input voltage rating of 105V.

Additional

features

include

Line

Under

Voltage

Lockout (UVLO), separate soft-start of main and

synchronous rectifier outputs, a timer for hiccup mode

current limiting, a precision reference, and thermal

shutdown.

Packages

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HTSSOP-20

•

WQFN-24

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Products conform to specifications per the terms of the Texas

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