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Synchronous buck-boost DC/DC controller uses single Inductor to provide high efficiency performance

December 13, 2010 // Paul Buckley

Synchronous buck-boost DC/DC controller uses single Inductor to provide high efficiency performance

Linear Technology Corporation has introduced a high efficiency (up to 98%) synchronous buck-boost DC/DC controller that operates from input voltages above, below or equal to the regulated output voltage. High power circuits that step-up and-down typically rely on transformers or two DC/DC converters, one for step-up (boost) and the other for step-down (buck) conversion.

The LTC3789 operates using a single inductor with 4-switch synchronous rectification and can deliver output power up to 150 W with a single device. Even higher output power can be achieved when multiple circuits are paralleled.

The LTC3789 operates with a selectable fixed frequency between 200 kHz and 600 kHz, and can be synchronized to an external clock over the same range with its integrated phase-locked loop (PLL). Its wide 4 V to 38 V input range, 0.8 V to 38 V output range and seamless transitions between operating modes make it ideal for a wide range of industrial controls, automotive, solar and high power battery-supplied systems.

The LTC3789 employs a proprietary current-mode control architecture for constant frequency operation in buck or boost mode and has powerful onboard quad N-channel MOSFET gate drivers.

The LTC3789 also provides an accurate, constant-current regulation loop for either input or output current, over a wide input voltage range. The input current limit function prevents overloading of the input source, and the output current limit provides an easy solution for regulated output current applications such as battery charger or LED drivers.

Fault protection is provided for overvoltage, overcurrent and short circuit conditions in all operating modes. In addition, the LTC3789 disconnects the input voltage from the output when in shutdown. The user can select continuous or pulse skip mode to maximize light load efficiency. Furthermore, the LTC3789 has adjustable soft-start, a power good output and maintains ±1.5% reference voltage accuracy over an operating junction temperature range of -40 to 125 °C.

Availability and Pricing

The LTC3789 is available in 28-pin 4 mm x 5 mm QFN and 28-lead SSOP packages. Pricing starts at $4.65 each in 1,000-piece quantities.

More information about the LTC3789 synchronous buck-boost DC/DC controller at

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