Wide input range step-down switching regulator

Linear Technology has introduced the LTC3851, a wide input range synchronous step-down switching regulator controller for driving N-channel power MOSFET stages. Thanks to a 4V to 38V input range, the device suits a variety of applications, including most intermediate bus voltages and battery chemistries in systems ranging from automotive to industrial, medical, to datacom and telecoms. Meanwhile, with output currents up to 20A and output voltages ranging from 0.8V to 5.5V, Linear claims the LTC3851 is ideal for point-of-load requirements.

The LTC3851 has a constant-frequency current mode architecture, enabling it to offer a selectable fixed or phase-lockable (PLL) frequency from 250kHz to 750kHz. A feature called OPTI-LOOP compensation allows the transient response to be optimised over a range of output capacitance and ESR values, including all ceramic capacitors designs.

Output current sensing is achieved by measuring the voltage drop across the output inductor (DCR) or by using an optional sense resistor. The current limit threshold voltage is also programmable. Current foldback provision limits MOSFET heat dissipation during short-circuit and over-load conditions. In addition, the LTC3851 has adjustable soft-start to control the turn-on time and manage inrush current, and a user controlled continuous current mode, to optimise load efficiency.

The LTC3851 has a 0.8V reference with an accuracy of 1% over a -40°C to 85°C operating temperature range. It is available in thermally enhanced 3mm x 3mm QFN-16 and narrow SSOP-16 packages.

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