1FEATURES

2• Internal Start-Up Bias Regulator

• 3A Compound Main Gate Driver

• Programmable Line Under-Voltage Lockout

(UVLO) with Adjustable Hysteresis

• Voltage Mode Control with Feed-Forward

• Adjustable Dual Mode Over-Current Protection

• Programmable Overlap or Deadtime between

the Main and Active Clamp Outputs

• Volt x Second Maximum Duty Cycle Clamp

• Programmable Soft-Start

• Current Sense Leading Edge Blanking

• Single Resistor Programmable Oscillator

• Oscillator Up / Down Sync Capability

• Precision 5V Reference

• Thermal Shutdown

PACKAGES

• TSSOP-16

• WSON-16 (5x5 mm) Thermally Enhanced

DESCRIPTION

The LM5025B is a functional variant of the LM5025

active clamp PWM controller. The functional

differences of the LM5025B are as follows:

The maximum PWM duty cycle is limited to less

than 75% to reduce voltage stress on the power

MOSFETs.

The CS2 hiccup mode threshold is increased to

0.5V

The CS2 filter discharge device is disabled

The VCC regulator continues to operate when the

line UVLO is below the threshold of normal

operation

The VREF regulator is switched off when the line

UVLO input falls below the operating threshold

The internal 5kΩ COMP pin pull-up resistor is

removed

The LM5025B PWM controller contains all of the

features necessary to implement power converters

utilizing 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 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.