A low, wide input voltage synchronous step-down DC/DC controller, the LTC3852, from Linear Technology has an onboard charge pump to provide 5V bias to drive low RDS(ON) and standard logic-level power MOSFETs from a 3.3V nominal supply. The input voltage range is 2.7 to 5.5V. Since the internal charge pump and DC/DC controller are independent, the charge pump output can provide 5V to power the internal gate drivers, and the DC/DC converter power stage can draw power from another source (up to 38V maximum). Output currents up to 25A can be supplied over an output from 0.8V to 99% of VIN for 3.3V-powered point-of-load applications. A constant-frequency current-mode architecture allows a selectable fixed or phase-lockable frequency from 250 to 750kHz. Selectable Burst Mode operation, pulse skip or forced continuous mode is user-controlled. Output current sensing is by measuring the voltage drop across the output inductor, or by using an optional sense resistor in series with the inductor. Current foldback limits heat dissipation during short-circuit and overload conditions. Soft-start or tracking controls the turn-on characteristics of the supply, and features a precision 0.8V reference with an accuracy of ±1.25% over -40 to 125°C. The controller is supplied in a thermally enhanced 3x5mm QFN-24 package.
