PWM Controller Services ISDN Power Supplies

Transformer design is said to be simplified and the need for external components reduced with the Si9113DY high-voltage PWM controller for ISDN power supplies. The chip provides multiple output dc-to-dc conversion for ISDN applications while meeting CCITT and ETR-080 requirements. Intended for systems requiring as much as 10W of power, the IC is used in power supplies for feature phones, PBX systems, modems, NT1 and NT1+ equipment, subscriber line interface circuits, and dc-to-dc conversion modules. Packaged in a 14-pin SOIC, the chip allows designers to implement a single-switch PWM circuit with a minimum of external parts. A wide input voltage range of 23.5V to 200V eliminates the need for an external start-up circuit. A 500-kHz internal oscillator provides a user-selectable 15-kHz to 250-kHz converter output frequency, further reducing capacitance requirements and allowing simpler, smaller magnetics designs. Pricing is $1.22 each/100,000.