Automotive Electronics

38V Synchronous Step-Down Controller Draws 50µA in Standby

Linear Technology Corporation introduces the LTC3807, a low quiescent current synchronous step-down dc-dc controller that draws only 50µA in standby mode with the output voltage in regulation. The 4V to 38V input supply range is designed to protect against high voltage transients, continue operation during automotive cold crank and cover a broad range of input sources and battery chemistries. The output voltage can be set from 0.8V to 24V at output currents up to 25A with efficiencies as high as 95%, making it well-suited for automotive, heavy equipment, industrial and robotic applications.

The LTC3807 has powerful 1.1 Ohm on-chip MOSFET gate drivers. It operates with a selectable fixed frequency between 50kHz and 900kHz and is synchronizable to an external clock ranging from 75kHz to 850kHz. The user can select from continuous operation, pulse skipping and low ripple Burst Mode® operation during light loads. Its current-mode architecture provides easy loop compensation, fast transient response and excellent line regulation.

Output current sensing is accomplished by measuring the voltage drop across the output inductor (DCR) for the highest efficiency or by using an optional sense resistor. Current foldback limits MOSFET heat dissipation during overload conditions. Additional features include a low 95ns minimum on-time for high step-down ratios, up to 99% duty cycle for low voltage dropout, an internal LDO that powers the gate drivers and a power good signal.

The LTC3807 is available in 20-pin 3mm x 4mm QFN and 20-lead TSSOP thermally enhanced packages. Four temperature grades are available, with operation from -40 to 125 degrees C for the extended and industrial grades, a high temp automotive range of -40 to 150 degrees C and a military grade of -55 to 150 degrees C. The 1,000-piece price starts at $2.30 each.

Linear Technology Corporation
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