DC/DC controller maintains voltage regulation in automotive systems

April 1, 2016

Milpitas, CA. Linear Technology Corp. has introduced the LTC7813, a dual output (boost + buck), low quiescent current synchronous DC/DC controller. When cascaded, its independent step-up (boost) and step-down (buck) controllers regulate the output voltage from an input voltage that can be above, below, or equal to the output voltage, including during an automotive load dump or cold crank.

Unlike conventional single inductor buck-boost regulators, the LTC7813’s cascaded boost + buck solution provides fast transient response with continuous, non-pulsating input and output currents. It substantially reduces ripple voltage and EMI, suitable for automotive, industrial, and high power battery operated systems.

The LTC7813 operates from an input voltage of 4.5 V to 60 V during start-up and maintains operation down to a 2.2-V input after start-up. The boost converter can produce an output voltage up to 60 V, and the buck converter produces an output voltage ranging from 0.8 V to 60 V with the entire system achieving an efficiency as high as 98%. In addition, this device can be configured for pass-through or wire mode with the synchronous boost MOSFET continuously on and the buck converter running at 99% duty cycle resulting in the input voltage being passed to the output with minimal voltage drop.

The LTC7813 can be configured for the vendor’s Burst Mode operation, reducing quiescent current to 29 µA with the buck channel on (34 µA for both on) in sleep mode, a useful feature for preserving battery run times. The 1-Ω onboard all N-channel gate drivers minimize MOSFET switching losses and provide an output current of more than 10 A per channel, limited only by external components. The output current for each converter is sensed by monitoring the voltage drop across the inductor (DCR) or by using a separate sense resistor.

The LTC7813’s current mode architecture enables a fixed selectable frequency from 50 kHz to 900 kHz, or it can be synchronized to an external clock from 75 kHz to 850 kHz. Additional features include adjustable gate drive voltage, soft-start or tracking, and foldback current limit, output overvoltage protection, run control, and a power-good output signal.

The LTC7813 is available in a 32-lead 5mm x 5mm QFN package. The 1,000-piece price starts at $4.82 each.

www.linear.com/product/LTC7813

About the Author

Rick Nelson | Contributing Editor

Rick is currently Contributing Technical Editor. He was Executive Editor for EE in 2011-2018. Previously he served on several publications, including EDN and Vision Systems Design, and has received awards for signed editorials from the American Society of Business Publication Editors. He began as a design engineer at General Electric and Litton Industries and earned a BSEE degree from Penn State.

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