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100V, Bidirectional Multiphase Synchronous Buck or Boost Controller

Ding Li - Senior Power Applications Engineer, Power Products Mar 31st 2017

Current 12V automotive systems are reaching their 3kW power limit due to the ever-increasing demand for more electrical devices. A newly proposed standard, LV148, combines a secondary 48V bus with the existing 12V system. Benefits of this technology include increased available energy that allows for more electrical circuits and a reduction in CO2 emissions. These systems require a bidirectional high current DC/DC controller to step-down or step-up the voltage between the 12V and 48V batteries in dual battery automotive applications. Target applications include automotive internal combustion cars, hybrid and mild hybrid vehicles.

The LTC3871 is a bidirectional synchronous buck or boost controller to step-down or step-up the voltage between the 12V and 48V batteries in dual battery automotive applications. The LTC3871 is a 100V/30V bidirectional two-phase synchronous buck or boost controller. It operates in buck mode or in boost mode. Either mode is configured on demand with an applied control signal. Up to 12 phases can be paralleled and clocked out-of-phase for high current applications up to 3kW. Four control loops, two for current and two for voltage, enable control of voltage and current on either the 48V or 12V outputs.

The device’s on-demand feature dynamically regulates the current in either direction. The LTC3871 operates at a selectable fixed frequency between 60kHz and 475kHz, and can be synchronized to an external clock over the same range. Additional features include overload and short-circuit protection, independent loop compensation for buck and boost, ±1% voltage regulation accuracy over temperature, as well as undervoltage and overvoltage lockout.

LTC3871 - Video Image