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Step-down controllers reduce component count

Posted: 14 Dec 2005     Print Version  Bookmark and Share

Keywords:Vishay Intertechnology  controller IC  MOSFETs 

Vishay Int. Inc. has released two synchronous buck step-down controller ICs designed to operate with external MOSFETs and a minimum of external components in DC/DC converter circuits that require output currents upwards of 10A.

The high-voltage SiP12201 and low-voltage SiP12202 controllers are designed to enable flexible, efficient voltage conversion in a broad range of applications in battery-powered, telecom and industrial end systems. The new devices' synchronous buck architecture allows voltages to be converted with efficiencies of 93 per cent, prolonging battery life while lowering heat in enclosed field-mounted or rack-mounted systems and reducing the need for cooling systems.

Input voltage range is 4.2V to 26V for the SiP12201 and 2.7V to 5.5V for the SiP12202. Adjustable output voltages for the two devices range from 0.6V to 20V for the SiP12201, and from 0.6V to 5.5V for the SiP12202. According to Vishay, the ability to reach 0.6V at the low end is a unique capability for a device with a 500kHz operating frequency and ensures the SiP12201 and SiP12202 will be able to satisfy the future requirements of lower voltages, predicted to decrease to 0.6V during the next decade.

Able to drive n-channel MOSFETs for both the high-side and low-side in a synchronous converter, the SiP12201 helps to reduce overall design costs by allowing the use of two lower-cost n-channel devices instead of one n-channel and one p-channel device. The SiP12201 also offers the advantage of 500kHz operation, which allows the use of smaller passive components in converter designs.

The low-voltage SiP12202 synchronous buck step-down controller is intended for power conversion in battery-powered electronics, as well as in notebook and desktop computers and a wide range of other systems using point-of-load or distributed power converters. This controller can be set to 100 per cent duty cycle to assure continued efficiency during low input-voltage conditions. In the event of a low-battery condition, the chip is able to operate as a low dropout (LDO) regulator by going to 100 per cent duty cycle.

The SiP12202 drives an n-channel MOSFET on the low side and a p-channel MOSFET on the high side. Use of the p-channel MOSFET on the high side eliminates the need for an external charge pump while also simplifying the high-side gate driver. High-frequency operation up to 500kHz enables use of smaller passive components for more compact end systems.

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