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Triple-output dc/dc controller safely powers pre-biased loads

Milpitas, Calif. — Linear Technology Corp. has introduced a highly efficient, triple-output, synchronous step-down switching regulator controller with coincident or ratiometric tracking that safely powers pre-biased loads. The LTC3853 is aimed at point-of-load regulation in datacom, telecom, set-top boxes, base stations, and multifunction printers, where multiple voltage rails must deliver high power with low heat dissipation in a small size.

The 4.5-V to 24-V (28-V max.) input range encompasses a wide variety of applications including most intermediate bus voltages. The on-board gate drivers power all N-channel MOSFET stages and can produce output currents up to 20 A per phase with output voltages ranging from 0.8 V to 13.5 V.

A constant-frequency, current-mode architecture allows a selectable fixed or phase-lockable (PLL) frequency from 250 kHz to 750 kHz. Power loss and supply noise are minimized by operating the three stages 120° out-of-phase. The LTC3853 can also be used in a 2+1 configuration, with output stages 1 and 2 180° out of phase. OPTI-LOOP compensation allows for a wide range of output capacitance and equivalent series resistance (ESR) values including all ceramic input and output capacitors.

The LTC3853 features a precision 0.8-V reference with an accuracy of ±1% over a -40°C to 125°C operating temperature range. With up to 98% duty cycle, the LTC3853 has a very low drop-out voltage, a useful feature for extending run times in battery-powered applications.

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 short-circuit and overload conditions.

In addition, the LTC3853 offers adjustable soft-start to control the turn-on time. Selectable burst mode operation, pulse skipping or continuous inductor current modes are user controlled to optimize light load efficiency vs. output ripple. The LTC3853 is offered in a thermally enhanced 6 x 6-mm QFN-40 package.

Pricing: Starts at $3.53 each in quantities of 1,000.

Datasheet: LTC3853

Linear Technology , www.linear.com

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