Electronic Design

Synchronous Step-Down DC-DC Controller Covers Wide Input Range

With a wide input range of 4 to 38 V, the LTC3854 synchronous step-down switching dc-dc controller drives N-channel power MOSFET stages. On-board MOSFET drivers enable high-power external MOSFETs to produce output currents up to 20 A with output voltages ranging from 0.8 to 5.5 V. A constant-frequency current-mode architecture provides a fixed 400-kHz operating frequency. The onboard 5-V regulator eliminates the need for a separate bias voltage to power the chip, while OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values, including all ceramic capacitor designs. Output current sensing measures the voltage drop across the output inductor (DCR) or an optional sense resistor. Current foldback limits MOSFET heat dissipation during short-circuit and overload conditions. Anti-shoot-through protection prevents shoot-through current in the power MOSFETs. Operating up to a 96% duty cycle, the controller has a very low dropout voltage for extending run times in battery-powered applications. The device features a precision 0.8-V reference with an accuracy of ±1% over the -40°C to 85°C operating temperature range. The LTC3854 comes in a 2- by 3-mm DFN-12 package and is available from stock with prices starting at $1.65 in 1000-piece quantities. LINEAR TECHNOLOGY CORP., Milpitas, CA. (408) 432-1900.



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