May 9, 2003-Maxim Integrated Products introduces the MAX8540 current-mode PWM controller and the MAX8541 voltage-mode PWM controller for isolated forward and flyback DC-DC converter modules (bricks). These controllers permit common PCB design for voltage-mode and current-mode converters to reduce engineering, inventory, and manufacturing costs.
The MAX8540/MAX8541 operate at 200kHz to 1MHz switching frequencies and synchronize to an external clock. These controllers permit optimization of magnetics design, providing an important performance advantage over competing products. An adjustable maximum duty cycle with voltage feed-forward reduces transformer size by maintaining a constant maximum primary volt-seconds over the input-voltage range. Adjustable slope compensation (MAX8540) and adjustable voltage ramp (MAX8541) allow further optimization of magnetics design.
Both controllers feature cycle-by-cycle, current-limit protection. The user can program the number of current-limited cycles needed to initiate the hiccup mode while at the same time ensuring startup into high-capacitance loads, which is a critical design challenge. The number of skipped cycles in hiccup mode can also be programmed to limit the power dissipation during a fault condition. Alternatively, the MAX8540/MAX8541 can also be programmed to latch off the controllers during fault conditions following a programmable delay or operate continuously in cycle-by-cycle current-limit mode.
The MAX8540/MAX8541 feature active-high and active-low enable controls and programmable undervoltage and overvoltage protection. It uses an integrated 9
gate driver for low-power designs or an external gate driver for high-power designs.
The MAX8540EEE/MAX8541EEE are available in space-saving 16-pin QSOP packages and are specified for the extended-industrial temperature range (-40°C to +85°C). Prices start at $1.75 (1000-up, FOB, USA). An evaluation kit is available to speed designs.
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