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Step-down dc/dc controller targets point-of-load requirements

Milpitas, Calif. — Linear Technology Corp. has introduced a synchronous step-down switching regulator controller with a wide input voltage range and coincident or ratiometric tracking. The LTC3851 drives all N-channel power MOSFET stages.

The 4-V to 38-V input range encompasses a wide variety of applications including most intermediate bus voltages and battery chemistries. The on-board MOSFET gate drivers allow the use of high-power external MOSFETs to produce output currents up to 20 A with output voltages ranging from 0.8 V to 5.5 V, making the LTC3851 suitable for point-of-load requirements. Applications include automotive, industrial, medical, datacommunications and telecom systems, multifunction printers and set-top boxes.

A constant-frequency current mode architecture provides a selectable fixed or phase-lockable (PLL) frequency from 250 kHz to 750 kHz . OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and equivalent series resistance (ESR) values including all ceramic capacitor designs. Output current sensing is accomplished by measuring the voltage drop across the output inductor (DCR) or by using an optional sense resistor. The current limit threshold voltage is programmable. Current foldback limits MOSFET heat dissipation during short-circuit and over-load conditions.

In addition, the LTC3851 offers adjustable soft-start to control the turn-on time and manage inrush current. Selectable Burst Mode operation, pulse skip mode or continuous current mode is user controlled to optimize light load efficiency vs. output ripple. The LTC3851 features a precision 0.8-V reference with an accuracy of ±1% over a-40°C to 85°C operating temperature range. With up to 99% duty cycle, the LTC3851 has a very low drop-out voltage, a useful feature for extending run times in battery-powered applications, Linear said.

The device is available in thermally enhanced 3 x 3-mm QFN-16 and narrow SSOP-16 packages.

Pricing: Starts at $1.71 each in quantities of 1,000.

Product information: LTC3851

Linear Technology , www.linear.com

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