Single-Inductor Low VIN Buck-Boost DC/DC Controller Optimized for Medium Power Outputs

Medium power buck-boost circuits have traditionally relied on transformers (SEPIC) or two cascaded DC/DC converters, one for the step-up (boost) and one for the step-down (buck) conversion. The LTC3785 requires only a single inductor from an input range of 2.7V to 10V, offers an identical output range, and can deliver up to 50W of output power. Operating with 4-switch synchronous rectification, the LTC3785 provides seamless transitions between the buck and boost operating modes.

The LTC3785’s proprietary topology and control architecture employs MOSFET RDS sensing for forward and reverse current limiting, yielding unrivaled efficiency. A sense resistor may be used when increased accuracy is desired. Moreover, the LTC3785 incorporates Burst Mode® operation which reduces light load quiescent current to less than 100uA, a valuable feature in battery powered systems. In addition, fault protection is provided for over voltage, over current and short circuit conditions in all operating modes. The operating frequency can be programmed from 100kHz to 1MHz with a single resistor and the LTC3785 also incorporates true output disconnect during shutdown.

The LTC3785 is offered in a 4mm x 4mm QFN-24 package.