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
- The VCC regulator continues to operate when the
line UVLO is below the threshold of normal operation
VREF regulator is switched off when the line UVLO input falls below the
- The internal 5kΩ COMP pin pull-up resistor is
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.
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