Current-Mode PWM Controllers with Integrated Startup Circuit

The MAX5019/MAX5020 integrate all the building blocks necessary for implementing DC-DC fixed-frequency power supplies. Either primary- or secondary-side regulation may be used to implement isolated or nonisolated power supplies. These devices are current-mode controllers with an integrated high-voltage startup circuit suitable for telecom/industrial voltage range power supplies. Current-mode control with leading-edge blanking simplifies control-loop design and internal ramp compensation circuitry stabilizes the current loop when operating at duty cycles above 50% (MAX5019). The MAX5019 allows 85% operating duty cycle and can be used to implement flyback converters whereas the MAX5020 limits the operating duty cycle to less than 50% and can be used in single-ended forward converters. A high-voltage startup circuit allows these devices to draw power directly from the 18V to 110V input supply during startup. The switching frequency is internally trimmed to 275kHz ±10%, thus reducing magnetics and filter component costs.

The MAX5019/MAX5020 are available in 8-pin SO packages.

Warning: The MAX5019/MAX5020 operate with high voltages. Exercise caution.

Applications

* Industrial Power Supplies * Isolated Power Supplies * Networking Power Supplies * Telecom Power Supplies

* Wide Input Range: (18V to 110V) or (13V to 36V)

* Isolated (without optocoupler) or nonisolated power supply

* Current-Mode Control

* Leading-Edge Blanking

* Internally Trimmed 275kHz ±10% Oscillator

* Low External Component Count

* Soft-Start

* High-Voltage Startup Circuit

* Pulse-by-Pulse Current Limiting

* Thermal Shutdown

* SO-8 Package