1 Features

1• Internal Start-Up Bias Regulator

• 3-A Compound Main Gate Driver

• Programmable Line Undervoltage Lockout (UVLO)

With Adjustable Hysteresis

• Voltage Mode Control With Feedforward

• Adjustable Dual Mode Overcurrent Protection

• Programmable Overlap or Dead Time Between

the Main and Active Clamp Outputs

• Volt × Second Clamp

• Programmable Soft Start

• Leading Edge Blanking

• Single Resistor Programmable Oscillator

• Oscillator UP and DOWN Sync Capability

• Precision 5-V Reference

• Thermal Shutdown

• Packages:

– 16-Pin TSSOP

– Thermally Enhanced 16-Pin WSON

(5 mm × 5 mm)

2 Applications

• Server Power Supplies

• 48-V Telecom Power Supplies

• 42-V Automotive Applications

• High-Efficiency DC-to-DC Power Supplies

3 Description

The LM5025A is a functional variant of the LM5025

active clamp PWM controller. The functional

differences of the LM5025A are that the CS1 and

CS2 current limit thresholds have been increased to

0.5 V, the internal CS2 filter discharge device has

been disabled and no longer operates each clock

cycle, and the internal VCC and VREF regulators

continue to operate when the line UVLO pin is below

threshold.

The LM5025A PWM controller contains all of the

features necessary to implement power converters

using the Active Clamp / Reset technique. With the

active clamp technique, higher efficiencies and

greater power densities can be realized compared to

conventional catch winding or RDC clamp / reset

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 1 MHz

and total PWM and current sense propagation delays

less than 100 ns. The LM5025A includes a highvoltage

start-up regulator that operates over a wide

input range of 13 V to 90 V. Additional features

include: line undervoltage lockout (UVLO), soft start,

oscillator UP and DOWN sync capability, precision

reference, and thermal shutdown.