Linear Technology controller enables conversion at up to 98% efficiency at 250W



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The LT8705 high-efficiency 80V Buck-Boost DC/DC Controller provides a regulated output current for a battery charger or current source.

With four feedback loops to regulate the input and output current and voltage, the LT8705 high-efficiency (up to 98%) synchronous buck-boost DC/DC controller from Linear Technology operates from input voltages above, below or equal to the regulated output voltage. The input current and voltage feedback loops can prevent overloading of solar cells. The output current loop provides a regulated output current for a battery charger or current source. The device can be used in a wide range of applications such as a voltage stabilizer in telecom and automotive requirements, as well as in solar or high impedance sources and battery systems. The controller operates over a wide 2.8V to 80V input voltage range and produces a 1.3V to 80V output, using a single inductor with 4-switch synchronous rectification. Output power up to 250W can be delivered with a single device. Higher output power can be achieved when multiple circuits are paralleled. The operating frequency is selectable between 100kHz and 400kHz, and can be synchronized to an external clock. The LT8705 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 user can select among forced continuous, discontinuous and Burst Mode® operation to maximize light load efficiency. The operating mode of the controller is determined through the MODE pin. The MODE pin can select among discontinuous mode, forced continuous mode and Burst Mode® operation. The LT8705 also features programmable UVLO and switching currents, along with input and output current monitoring with programmable maximum levels. Additional features include servo pins to indicate which feedback loops are active, a 3.3V/12mA LDO, adjustable soft-start, onboard die temperature monitor and ±1% reference voltage accuracy over an operating junction temperature range of -40°C to 125°C. The LT8705 is available in a 38-pin 5mm x 7mm QFN, and also a 38-lead TSSOP package with additional pin spacing for high voltage operation. Linear Technology