Analog Devices Inc./Maxim Integrated

The LTC1877 s a high efficiency monolithic synchronous buck regulator using a constant-frequency, current mode architecture. Supply current during operation is only 10μA and drops to < 1μA in shutdown. The 2.65V to 10V input voltage range makes the LTC1877 ideally suited for both single and dual Li-Ion battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems.Switching frequency is internally set at 550kHz, allowing the use of small surface mount inductors and capacitors. For noise sensitive applications the LTC1877 can be externally synchronized from 400kHz to 700kHz. Burst Mode operation is inhibited during synchronization or when the SYNC/MODE pin is pulled low, preventing low frequency ripple from interfering with audio circuitry.The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.8V feedback reference voltage. The LTC1877 is available in a space saving 8-lead MSOP package. Lower input voltage applications (less than 7V abs max) should refer to the LTC1878 data sheet.ApplicationsCellular TelephonesWireless ModemsPersonal Information AppliancesPortable InstrumentsDistributed Power SystemsBattery-Powered Equipment

The LTC1879 is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. Operating supply current is only 15µA with no load and drops to <1µA in shutdown. The input supply voltage range of 2.65V to 10V makes the LTC1879 ideally suited for both single and dual Li-Ion battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems.The switching frequency is internally set to 550kHz, allowing the use of small surface mount inductors and capacitors. For noise sensitive applications, the LTC1879 can be externally synchronized from 350kHz to 750kHz. Burst Mode operation is inhibited during synchronization or when the SYNC/MODE pin is pulled low.The internal synchronous rectifier switch increases efficiency and eliminates the need for an external Schottky diode. Low output voltages are easily supported with a 0.8V feedback reference voltage. The LTC1879 is available in a 16-lead SSOP package.ApplicationsCellular TelephonesPortable ComputersWireless Modems

The LTC1909-8 is a synchronous step-down switching regulator controller with a digitally programmable output voltage. The output voltage is selected from one of two 5-bit settings programmed into internal registers via a 2-wire SMBus/I²C interface. The interface features safeguards against invalid output voltages and allows the microprocessor to turn the regulator on and off. Valley current control delivers very low duty cycles without requiring a sense resistor. Operating frequency is selected by an external resistor and is compensated for variations in VINand VOUT.Discontinuous mode operation provides high efficiency operation at light loads. A forced continuous control pin reduces noise and RF interference and can assist secondary winding regulation by disabling discontinuous mode operation when the main output is lightly loaded.Fault protection is provided by internal foldback current limiting, an output overvoltage comparator and optional short-circuit shutdown timer.The LTC1909-8 is available in the 28-lead SSOP package.ApplicationsPower Supplies for DSPs, ASICs, FPGAs and CPUsVoltage Margining

The LTC1928-5 is a doubler charge pump with an internal low noise, low dropout (LDO) linear regulator. The part is designed to provide a low noise boosted supply voltage for powering noise sensitive devices such as high frequency VCOs in wireless applicationsAn internal charge pump converts a 2.7V to 4.4V input to a boosted output, while the internal LDO regulator converts the boosted voltage to a low noise regulated output. The regulator is capable of supplying up to 30mA of output current. Shutdown reduces the supply current to <8µA, removes the load from VINby disabling the regulator and discharges VOUTto ground through a 200Ω switch.The LTC1928-5 LDO regulator is stable with only 2µF on the output. Small ceramic capacitors can be used, reducing PC board area.The LTC1928-5 is short-circuit and overtemperature protected. The part is available in a 6-pin low profile (1mm) ThinSOT package.ApplicationsVCO Power Supplies for Cellular Phones2-Way PagersWireless PCMCIA CardsPortable Medical InstrumentsLow Power Data AcquisitionRemote TransmittersWhite LED DriverGaAs Switches

The LTC1929/LTC1929-PG are 2-phase, single output, synchronous step-down current mode switching regulator controllers that drive N-channel external power MOSFET stages in a phase-lockable fixed frequency architecture. The 2-phase controllers drive their two output stages out of phase at frequencies up to 300kHz to minimize the RMS ripple currents in both input and output capacitors. The 2-phase technique effectively multiplies the fundamental frequency by two, improving transient response while operating each channel at an optimum frequency for efficiency. Thermal design is also simplified.An internal differential amplifier provides true remote sensing of the regulated supply’s positive and negative output terminals as required by high current applications.The RUN/SS pin provides soft-start and a defeatable, timed, latched short-circuit shutdown to shut down both channels. Internal foldback current limit provides protection for the external synchronous MOSFETs in the event of an output fault. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values.ApplicationsDesktop ComputersInternet/Network ServersLarge Memory ArraysDC Power Distribution Systems