New DC/DC Controller That Maintains Regulation During Engine Restarts

The Linear Technology LTC3899 ensures Voltage Regulation is Maintained Over a 2.2V to 60V Input Range

Linear Technology (now part of Analog Devices) has released the LTC3899, a triple output (buck, buck, boost) 29µA quiescent current, synchronous DC/DC controller that maintains output voltage regulation over a 2.2V to 60V input range. A 12V car battery can droop to less than 4 volts during engine restart or cold crank, causing reset of infotainment systems and other electronics that operate from 5 volts and higher. The boost converter feeds two stepdown converters, avoiding output voltage dropout when a car battery droops, a useful feature in automotive start/stop systems that shut off the engine at idle to save fuel. The 60V maximum input voltage covers double battery truck applications. Alternatively, the buck controllers can be powered from the input as a general purpose triple output controller.

The LTC3899 operates from an input voltage of 4.5V to 60V during startup and maintains operation down to 2.2V after startup. The boost and buck converters can produce output voltages up to 60V with efficiencies as high as 95%. In applications where the input voltage may exceed the regulated output voltage, the LTC3899 keeps the synchronous boost MOSFET on continuously so that the output voltage follows the input voltage with minimal power loss.

In addition, the LTC3899 can be configured for Burst Mode® operation, reducing quiescent current to 29µA for one channel (39µA for all three channels on) with outputs in regulation in standby mode, a useful feature for preserving battery run times. The powerful 1ohm onboard all Nchannel gate drivers minimize MOSFET switching losses and provide for output currents of more than 10 amps per channel, limited only by external components. Furthermore, the output current for each converter can be sensed by monitoring the voltage drop across the inductor (DCR) or by using a sense resistor. The LTC3899's constant frequency current mode architecture enables a fixed frequency from 50kHz to 900kHz or it can be synchronized to an external clock from 75kHz to 850kHz. Additional features include an onboard LDO for IC power and gate drive, output voltage tracking or adjustable softstart, a power good signal and an optional external V bias input.

Technical Specifications of the LTC3899 DC/DC Controller

The LTC3899 is currently available in a SSOP38 and QFN38 Package and can be ordered from Analog Devices in tube or reel packaging.

For more information on the LTC3899 Synchronous DC/DC Controller, visit the Analog Devices website at Linear Technology LTC3899 product page.

The Analog Devices website address is www.analog.com
[Reprinted with kind permission from Linear Technology - Release Date: 27th January, 2015]