MAX5974 PWM Controller

MAX5974 PWM Controller Maxim introduced its MAX5974 - a high-frequency current-mode PWM controller with an active-clamp architecture and spread-spectrum operation. The device's active-clamp topology delivers better than 90% efficiency, thus reducing power consumption in synchronous forward/flyback power supplies. The MAX5974A/MAX5974C versions are well suited for universal rectified offline (85V to 265V) or telecom (36V to 72V) input voltages. The MAX5974B/MAX5974D also accommodate input voltages as low as 10.5V, for example, adapters. The MAX5974A/MAX5974B contain an internal sample-and-hold error amplifier that regulates the output voltage through a coupled inductor. This feedback configuration saves space and cost by eliminating the need for a shunt regulator, optocoupler, and tertiary winding for the bias circuits. Applications requiring optocoupler feedback can use the MAX5974C/MAX5974D, which have a feedback input connected in series. The device's switching frequency is adjustable from 100kHz to 600kHz and is trimmed to provide ±8% accuracy. This allows designers to optimize the magnetics and filter elements used in the circuit to meet EMI requirements. The duty cycle can be programmed up to 80% of the maximum duty-cycle limit. Additional features include an enable input to shutdown the device and programmable soft-start to eliminate output-voltage overshoot. The MAX5974A/MAX5974C have an internal bootstrap ULVO with high hysteresis that requires 20V for startup; the MAX5974B/MAX5947D require 10V for startup. Rated for operation in an extended temperature range of over -40 degrees Celsius to +85 degrees Celsius, the MAX5974 is available in a 3mm x 3mm, 16-pin TQFN package.

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