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38VIN Dual Synchronous Step-Down DC/DC Controller with 1% Accurate Pin-Selectable Output Voltages

23rd February 2010

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Linear Technology Corporation announces the LTC3865/-1, a 95% efficient, dual output synchronous step-down DC/DC controller with 2-pin selectable VOUT programming, a feature that saves 4 precision feedback resistors. The output voltages maintain a tight ±1% accuracy including initial set-point, a -40°C to 125°C operating temperature range and load/line regulation. Nine selectable output voltages ranging from 0.6V to 5V are possible. The 4.5V to 38V input voltage range encompasses a wide variety of applications including most intermediate bus voltages and battery chemistries. The strong on-board N-channel MOSFET driver enables the use of high power external MOSFETs to produce output currents as high as 20A. Applications include point-of-load regulators in medical, industrial, automotive, datacom, telecom and multifunction printers.

A constant-frequency current mode architecture allows a selectable fixed or phase-lockable (PLL) switching frequency from 250kHz to 770kHz. Power loss and supply noise are minimized by operating the stages 180° out-of-phase. OPTI-LOOP® compensation reduces the transient response and can be optimized over a wide range of output capacitance and ESR values, including all ceramic input and output capacitors. Output current sensing is accomplished by measuring the voltage drop across the output inductor (DCR) for maximum efficiency or by using an optional sense resistor. Current foldback limits MOSFET heat dissipation during short-circuit conditions. In addition, the LTC3865/-1 has adjustable soft-start or tracking to control the output voltage start-up characteristics. With capability up to 99% duty cycle, the LTC3865/-1 has a very low drop-out voltage, a useful feature for extending run times in battery powered applications.