MAX5974D Datasheet | Maxim Integrated

.. 19-5331; Rev 0; 6/10 Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers General Description The MAX5974_ provide control for wide-input-voltage, active-clamped, current-mode PWM, forward converters in Power-over-Ethernet (Po E) powered device (PD) applications. The MAX5974A/MAX5974C are well-suited for universal or tele input range, while the MAX5974B/ MAX5974D also acmodate low input voltage down to 10.5V. The devices include several Features to enhance supply efficiency. The AUX driver recycles magnetizing current instead of wasting it in a dissipative clamp circuit. Programmable dead time between the AUX and main driver allows for zero-voltage switching (ZVS). Under lightload conditions, the devices reduce the switching frequency (frequency foldback) to reduce switching losses. The MAX5974A/MAX5974B feature unique circuitry to achieve output regulation without using an optocoupler, while the MAX5974C/MAX5974D utilize the traditional optocoupler feedback method. An internal error amplifier with a 1% reference is very useful in nonisolated design, eliminating the need for an external shunt regulator. The devices feature a unique feed-forward maximum duty-cycle clamp that makes the maximum clamp voltage during transient conditions independent of the line voltage, allowing the use of a power MOSFET with lower breakdown voltage. The programmable frequency dithering feature provides low-EMI, spread-spectrum operation. The MAX5974_ are available in 16-pin TQFN-EP packages and are rated for operation over the -40°C to +85°C temperature range. Features S Peak Current-Mode Control, Active-Clamped Forward PWM Controller S Regulation Without Optocoupler (MAX5974A/ MAX5974B) S Internal 1% Error Amplifier S 100k Hz to 600k Hz Programmable Q8% Switching Frequency, Synchronization Up to 1.2MHz S Programmable Frequency Dithering for Low-EMI, Spread-Spectrum Operation S Programmable Dead Time, PWM Soft-Start, Current Slope pensation...