2010

DC/DC Controller

Linear Technology (Milpitas, CA) has released the LTC3890/-1 highvoltage, dual-output, synchronous step-down DC/DC controller that draws 50μA when one output is active, and 60μA when both outputs are enabled. With both outputs shut down, the LTC3890/-1 draws 14μA. The 4V to 60V input supply range protects against high-voltage transients, continues operation during automotive cold crank, and covers a range of input sources and battery chemistries. Each output can be set from 0.8V to 24V at output currents up to 20 amps with efficiencies as high as 95%, making it suitable for 12V or 24V automotive, heavy equipment, industrial control, robotics, and telecom applications.

altThe controller has 1.1-ohm on-chip MOSFET gate drivers, operates with a selectable fixed frequency between 50 kHz and 900 kHz, and can be synchronized to an external clock from 75 kHz to 850 kHz with its phased-locked loop (PLL). The user can select from continuous operation, pulse skipping, and low-ripple Burst Mode® operation during light loads. Output current sensing is accomplished by measuring the voltage drop across the output inductor (DCR), or by using an optional sense resistor. Current foldback limits MOSFET heat dissipation during overload conditions. The device is available in two versions: the LTC3890 includes a clock out, clock phase modulation, two separate power good outputs, and adjustable current limit; and the LTC3890 is available in a 32-lead 5 × 5-mm QFN package.

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