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Synchronous Boost Controller with up to 98% Efficiency Eliminates Heat Sink

6th January 2011

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Datasheet

Linear Technology has announced the LTC3786, a synchronous step-up DC/DC controller that replaces the boost diode with a high efficiency N-channel MOSFET. This eliminates the heat sink normally required in medium to high power boost converters. In applications where the input voltage may exceed the regulated output voltage, the LTC3786 is able to keep the synchronous MOSFET on continuously so that the output voltage follows the input voltage with minimal power loss. The LTC3786's low 55µA quiescent current extends the run time in battery-powered applications when in standby mode. This controller can produce a 24V at 5A output from a 12V input with up to 98% efficiency, making it ideal for automotive, industrial, and medical applications where a step-up DC/DC converter must have low heat dissipation in a small solution size.

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

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

The LTC3786 is available in a thermally enhanced MSOP-16 package and a 3mm x 3mm QFN.

Summary of Features of the LTC3786:

* Up to 98% Efficiency

* Eliminates Heat Sink in Medium to High Power Boost Converters

* Up to 60V VOUT Operation

* Wide VIN Ranging from 4.5V to 38V, Maintains Operation down to 2.5V After Start-Up

* Low 55µA Quiescent Current Extends the Run-Time in Battery-Powered Applications

* 8µA Shut Down Current

* Powerful 1.2 Ohm Gate Drivers

* 100% Duty Cycle Capability for Synchronous MOSFET

* Phase Lockable Frequency from 75kHz to 850kHz

* Programmable Fixed Frequency from 50kHz to 900kHz

* RSENSE or Inductor DCR Current Sensing

* Current Mode Control

* ±1% Reference Voltage Accuracy over -40oC to +125oC

* Programmable Soft-Start

* Power Good Output