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

Oct 3 2007 -MILPITAS, CA
  • Linear Technology Corporation introduces the LTC3785, a 96% efficient buck-boost switching regulator controller that operates from input voltages above, below or equal to the output voltage for powering tablet PCs, handheld instruments, wireless modems, portable media players and a wide variety of single or dual-cell Li-Ion or multi-cell alkaline/NiMH powered devices.

    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 × 4mm QFN-24 package. The 1,000-piece price is $3.56 each.

    Summary of Features: LTC3785

    • Single Inductor Architecture Allows Operation with the Input Voltage Above, Below or Equal to the Output Voltage
    • 2.7V to 10V Input and Output Voltage Range
    • 4-Switch, Synchronous Operation for up to 96% Efficiency
    • RDS Current Sensing Enhances Efficiency
    • 100uA No Load Quiescent Current
    • 100kHz to 1MHz Programmable Constant Frequency Operation
    • Over Voltage and Over Current Protection
    • True Output Disconnect During Shutdown
    • All N-Channel MOSFET Power Switches

    10V Single Inductor Synchronous Buck-Boost Controller


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