Off-Line Switcher IC Allows For Reduced Component Count

The TinySwitch-II family of monolithic ICs integrates a high voltage power MOSFET, oscillator and control circuitry onto a single CMOS chip and consists of eight part types ranging in power levels from 4W to 23W. Built-in features include auto-restart for short circuit and open loop fault protection, frequency jittering for low EMI filtering cost, current limit and thermal protection, and programmable line under-voltage detection preventing power on/off glitches. The internal switching frequency of 132 kHz reduces transformer size and allows the use of lower cost EF12.6 or EE13 cores. Applications for this family of ICs includes low power adapters for portable equipment such as cell phones, PDAs, digital cameras, external computer peripherals, and power tools and standby power supplies found in PCs, white goods, and audio/video equipment. Prices range from $0.74 each/1,000 for the TNY264P, a 5.5W part housed in a plastic eight-pin DIP to $1.09 each for the 23W rated TNY268G housed in a surface-mountable 8-pin SMD package. Design tools are available through the company's website.