Maxim PWM controller eyes dc-dc, ac-ac power supplies

The MAX5069 dual-output, high-frequency, current-mode PWM controller from Maxim Integrated Products is designed for isolated telecom dc-dc or universal, off-line input ac-ac power supplies, and allows the design of half-bridge, full-bridge, and push-pull power supplies.

The controller's switching frequency is programmable from 50kHz to 2.5MHz using an external-programming resistor. The switching frequency is also internally trimmed to ±4.5 percent accuracy, eliminating the need to oversize the magnetic components.

The MAX5069's turn-on/turn-off voltages can be precisely programmed using external resistors, while an integrated, digital softstart guarantees a monotonic rise on the power-supply output and eliminates overshoot during power up.

With a programmable, integrating-fault-protection circuit that provides robust fault protection, the device prevents component overheating by turning off the power supply in the event of sustained overcurrent conditions or when there is a direct short circuit at the power-supply output. An internal error amplifier with a ±2 percent accurate reference enables isolated power supplies with primary- or secondary-side regulation to be designed. The controller can also be synchronized to an external clock, thus eliminating beat-frequency effects when running multiple power supplies in a system.

The MAX5069's 50?A startup current allows the 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, and current-sense threshold is 320mV. Rated for operation between the -40°C and 125°C temperature range, the product is available in a thermally enhanced, 16-pin TSSOP package for $1.48.