Synchronous Boost Controller Eliminates Heat Sink

Linear TechnologyCorp.'s LTC3786 is a synchronousstep-up dc/dc controller that replaces the boost diode with a high efficiencyN-channel MOSFET. This eliminates the heat sink normally required in medium tohigh power boost converters. In applications where the input voltage may exceedthe regulated output voltage, the LTC3786 is able to keep the synchronousMOSFET on continuously so that the output voltage follows the input voltagewith minimal power loss. The LTC3786's low 55AmuA quiescent current extends therun time in battery-powered applications when in standby mode. This controllercan produce a 24V at 5A output from a 12V input with up to 98 percentefficiency, making it useful for automotive, industrial and medicalapplications where a step-up dc/dc converter must have low heat dissipation ina small solution size.

The LTC3786 operates from an input voltage ranging from 4.5V to 38V duringstart-up, maintaining operation down to 2.5V after start-up and can regulate anoutput voltage as high as 60V. The 1.2 Ohm onboard N-channel MOSFET gatedrivers are capable of slewing large MOSFET gates quickly, minimizingtransition losses and allowing for up to a 10A output current.

The LTC3786 has adjustable cycle-by-cycle current limit protection and useseither a sense resistor or monitors the voltage drop across the inductor (DCR)for current sensing. The LTC3786 has a phase-lockable switching frequency rangeof 75kHz to 850kHz and a fixed frequency operating range from 50kHz to 900kHz. TheLTC3786 has adjustable soft-start and maintains +1 percent referencevoltage accuracy over an operating temperature range of
-40 to 125C.

The LTC3786 is available in a thermally enhanced MSOP-16 package and a 3 x 3 mmQFN. The 1,000-piece price starts at $2.80 each and is available from stock.

Synchronous Boost Controller Eliminates Heat Sink