LTC3728 Series

The LTC3728 is a dual high performance step-down switching regulator controller that drives all N-channel synchronous power MOSFET stages. A constant-frequency current mode architecture allows phase-lockable frequency of up to 550kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase.OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The precision 0.8V reference and power good output indicator are compatible with future microprocessor generations, and a wide 3.5V to 30V (36V maximum) input supply range encompasses all battery chemistries.A RUN/SS pin for each controller provides both softstart and optional timed, short-circuit shutdown. Current foldback limits MOSFET dissipation during short-circuit conditions when overcurrent latchoff is disabled. Output overvoltage protection circuitry latches on the bottom MOSFET until VOUTreturns to normal. The FCB mode pin can select among Burst Mode, constant-frequency mode and continuous inductor current mode or regulate a secondary winding. The LTC3728 includes a power good output pin that indicates when both outputs are within 7.5% of their designed set point.Vin RangeVref AccyCurrent Limit Latch Off3.3V LDO AvailableLTC37283.5V to 36V+/-1%YesLTC3728L4.5V to 28V+/-1%YesYesLTC3728LX4.5V to 28V+/- 1.5%YesYesLTC3728L-14.5V to 28V+/- 1.5%Foldback onlyYesApplicationsNotebook and Palmtop ComputersTelecom SystemsPortable InstrumentsBattery-Operated Digital DevicesDC Power Distribution Systems