Linear Technology LTC3789 buck-boost DC/DC controller

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Linear Technology has released the LTC3789, 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 device operates using a single inductor with four-switch synchronous rectification and can deliver power to 150 W with a single device. Even higher output power can be achieved when multiple circuits are paralleled.

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

The device employs a current-mode control architecture for constant frequency operation in buck or boost mode and has powerful onboard quad N-channel MOSFET gate drivers. It 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, it disconnects the input voltage from the output when in shutdown. The user can select continuous or pulse skip mode to maximise 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.