Step-Down DC/DC Controller in 4 x 4 QFN from Linear Technology

Applications include notebook and tablet PCs, portable instruments, datacom, telecom, set-top boxes, basestations, and multifunction printers where a step-down DC/DC converter must deliver high power with low heat dissipation in a small solution size.

A constant-frequency current mode architecture allows a selectable fixed or phase-lockable (PLL) frequency from 250kHz to 780kHz. Power loss and supply noise are minimized by operating both stages 180° out-of-phase. OPTI-LOOP® compensation allows the transient response to 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) or by using an optional sense resistor. Current foldback limits MOSFET heat dissipation during short-circuit conditions. In addition, the LTC3850 has adjustable soft-start to control the turn-on time. Selectable Burst Mode® operation, pulse skipping mode or continuous inductor current mode is user controlled to optimize light load efficiency vs. output ripple. The LTC3850 features a precision 0.8V reference with an accuracy of ±1% over a -40°C to 85°C operating temperature range. With up to 97% duty cycle, the LTC3850 has a very low drop-out voltage, a useful feature for extending run times in battery powered applications.

The LTC3850 is offered in a thermally enhanced 4mm x 4mm QFN-28 and SSOP-28 packages. Pricing for 1,000-piece quantities begins at $2.40 each.