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Pulse width modulation controller

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MAXIM Integrated Products, represented by Arrow Electronics , has released the MAX5068, a high-frequency, current-mode, pulse-width modulation (PWM) controller for isolated telecom dc-dc or universal off-line input ac-dc power supplies.

Both flyback and forward-converter designs can be realized using the MAX5068. The device's switching frequency is programmable from 12.5kHz to 1.25Mhz by using an external-programming resistor. The switching frequency is also internally trimmed to ±4% accuracy, eliminating the need to oversize the magnetic components. The MAX5068's turn-on/turn-off voltages can be precisely programmed using external resistors. Integrated, digital softstart guarantees a monotonic rise on the power-supply output and eliminates overshoot during power up.

The MAX5068's programmable integrating-fault-protection circuit provides robust fault protection. This feature prevents component overheating by turning off the power supply in the case of sustained overcurrent conditions or when there is a direct short circuit at the power-supply output.

An internal error amplifier with a ±2% accurate reference enables the design of isolated power supplies with primary or secondary-side regulation. The device can be synchronized to an external clock, eliminating beat-frequency effects when running multiple power supplies in a system.

The MAX5068's 50 μA startup current allows use of a high-value startup resistor, thereby reducing power loss across the startup resistor in standby mode. The device's gate-driver output is capable of sourcing or sinking 1A. In addition, the current-sense threshold is 320mV. These features allow the design of high-power and high-efficiency power supplies. Moreover, the cycle-by-cycle current-limit propagation delay is 40ns, which allows a fast turn-off of the power supply during output short-circuit conditions.

Rated for operation over a wide -40°C to +125°C range, the MAX5068 is available in a thermally enhanced 16-pin TSSOP package.

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