Buck-Boost regulator 98% efficient
24 February 2009
High voltage DC/DC system also saves space
Linear Technology Corporation extends its family of buck-boost DC/DC uModule regulator systems with the introduction of a third pin-compatible product, the LTM4609, a high voltage and high efficiency DC/DC system in a surface mount 15 mm x 15 mm x 2.8 mm LGA (land grid array) package.
The LTM4609 integrates a synchronous buck-boost DC/DC controller, four N-channel MOSFETs, input and output bypass capacitors and the compensation circuitry in a small plastic molded package. Only an inductor, feedback and sense resistors and bulk capacitors are required to implement a very low profile, compact and high efficiency design. The device has applications in point-of-load and intermediate-bus regulation in networking, industrial and automotive systems and high power battery-operated devices.
The LTM4609 regulates an output voltage from a variable input voltage greater than, less than or equal to the output voltage. The device operates from 4.5 VIN to 36 VIN and regulates an output voltage from 0.8 V to 34 V and can deliver an output power up to 120 W.
The LTM4609’s onboard proprietary 4-switch synchronous MOSFET design enables up to 98.3% efficiency in boost mode and 97.3% efficiency in buck mode (condition: VIN: 6.5 V to 36 V, VOUT: 30 V, IOUT: 2 A). Unlike SEPIC (Single Ended Primary Inductor Converter) topologies requiring as many as 20 components and custom magnetics, the LTM4609 uses only six external components, including an off-the-shelf inductor, ensuring a very simple PCB layout. Comparable SEPIC circuits achieve lower efficiency in the range of 76% to 84%.
In order to reduce undesirable frequency harmonics, the LTM4609 is phase-lockable to an external clock frequency ranging from 200 kHz to 400 kHz. Safety features include overvoltage and foldback current protection. The LTM4609 is offered for operation from -40ºC to 85ºC with 125ºC maximum junction temperature.
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