New Non-Isolated Buck/Boost Converter IC Simplifies ISDN Power Supply Designs

MALVERN, PENNSYLVANIA - April 12, 2000 - A new non-isolated buck/boost converter IC that gives designers a simple and compact way to convert a -48-V input to +3.3 V or +5 Vin ISDN digital phones was released today by Vishay Intertechnology. The new Vishay Siliconix Si9121DY allows component count to be reduced by over 20% compared with typical solutions, with a complete converter design requiring just 10 passives and a single Schottky diode as the external components.

Packaged in a narrow-body SOIC-8, the Si9121DY features an integrated high-voltage start-up circuit, 95-kHz oscillator, and 70-V n-channel depletion MOSFET that simplify converter designs and reduce external parts count. An integrated floating feedback error amplifier eliminates the need for an external shunt regulator by providing direct output regulation to within 4% tolerance at all line, load, and industrial temperature conditions. No transformer is required.

Designed to work efficiently across the entire input voltage range of -10 V to -60 V, the Si9121DY provides efficiencies of greater than 70% when converting a -48-V input voltage to +3.3 V at 400 mA, and of greater than 60% when converting a -60-V input under light load conditions to +5 V at 25 mA.

In addition to thermal shutdown and cycle-by-cycle current limiting features, the Si9121DY provides a built-in hiccup mode timer that allows the device to handle a continuous output short-circuit and to automatically restart when the short-circuit is removed. An industry-first for this device type, the hiccup mode timer draws only milliwatts of power from the source and eliminates the need for an external component to handle the restart function.

"The Si9121DY provides an easy implementation thanks to the minimal number of required external control components," said Tony Armstrong, Marketing Director at Vishay Intertechnology. "It thus significantly reduces the cost of a total converter solution, for which Vishay provides the total bill-of-materials of passive and active components." In addition to digital phones, the Si9121DY will be used to regulate ISDN power supplies for DC-to-DC converter modules, PBX systems, SLIC circuits, and modems. Two available versions of the device give designers a choice of either a +5-V (Si9121DY-5) or +3.3-V (Si9121DY-3) fixed output.

Samples and production quantities of the Si9121DY are available now, with lead times of 10 weeks for larger orders.

Vishay Intertechnology, Inc., a Fortune 1,000 Company listed on the NYSE (VSH), is one of the world's largest manufacturers of discrete semiconductors (diodes, rectifiers, transistors, and optoelectronics and selected ICs) and passive electronic components (resistors, capacitors, inductors, sensors, and transducers). These components are used in virtually all types of electronic devices and equipment, in the industrial, computing, automotive, consumer, telecommunications, military, aerospace, and medical markets. Its product innovations, successful acquisition strategy, and ability to provide "one-stop shop" service have made Vishay a global industry leader. Vishay can be found on the Internet at http://www.vishay.com.