A 12V car battery can experience a voltage drop to less than 4V during a fresh engine start or cold start, causing infotainment systems and other electronics that operate at 5V or higher to restart. The boost converter feeds two buck converters, preventing a drop in output voltage when the car battery voltage drops—a useful feature in automotive start/stop systems that shut off the engine when the vehicle is stationary to save fuel. The maximum input voltage of 60V is intended for truck applications with two batteries. The buck converters can also be fed into 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 from 2.2V thereafter. The boost and buck converters can generate output voltages up to 60V with efficiencies up to 95%. In applications where the input voltage may exceed the regulated output voltage, the LTC3899 keeps the synchronous boost MOSFET continuously on, so the output voltage follows the input voltage with minimal power loss.
Furthermore, the LTC3899 can be configured to operate in Burst Mode®, reducing the quiescent current to 29 µA for one channel (39 µA when all three channels are active) with regulated outputs in standby mode—a useful feature for conserving battery runtime. The powerful 1-ohm resistor built into all N-channel gate drivers minimizes MOSFET switching losses and delivers output currents exceeding 10 A per channel, limited only by external components. Additionally, the output current for each converter can be detected by monitoring the voltage drop across the inductor (DCR) or using a sensing resistor. The LTC3899's constant-frequency current-mode architecture allows for a fixed frequency from 50kHz to 900kHz or synchronization to an external clock from 75kHz to 850kHz. Other features include an LDO regulator for power and IC gate control, output voltage tracking or adjustable soft start, a power correct signal, and an optional external VCC bias input.
The LTC3899 is available in 38-pin SSOP and 5mm x 7mm QFN packages. Four temperature ratings are available: an extended-range and industrial version for operation between -40°C and 125°C, a high-temperature automotive version from
-40°C to 150°C, and a military version from -55°C to 150°C.
- Details
- Category: Integrated Circuits
60V DC/DC buck/buck/boost controller with triple output and a quiescent current of 29µA
Linear Technology Corporation announces the LTC3899, a synchronous DC/DC controller with triple output (buck, buck, boost) and a quiescent current of 29µA that maintains output voltage regulation for an input range of 2.2V to 60V.
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