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.