LM5025B

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 V_CC regulator continues to operate when the line UVLO is below the threshold of normal operation
• The V_REF 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.