Automotive & Transportation

Boost + Buck Synchronous DC/DC Controller Regulates Automotive Systems

01 April 2016

The LTC7813 from Linear Technology Corporation is 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.

LTC7813 boost + buck synchronous DC/DC controller. Source: Linear Technology.LTC7813 boost + buck synchronous DC/DC controller. Source: Linear Technology.

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, ideal 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 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 1Ω onboard all N-channel gate drivers minimize MOSFET switching losses and provide an output current of more than 10 amps per channel, limited only by external components.

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 fold-back current limit, output overvoltage protection, run control and a power-good output signal.

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

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