Analog Devices Inc./Maxim Integrated

The LTC3538 is a highly efficient, low noise, buck-boost DC/DC converter that operates from input voltages above, below, and equal to the output voltage. The topology incorporated in the IC provides a continuous transfer function through all operating modes, making the product ideal for single Lithium Ion or multicell Alkaline or NiMH applications where the output voltage is within the battery voltage range.The LTC3538 is suited for use in Micro Hard Disk Drive (µHDD) applications with its 800mA current capability. Burst Mode®operation provides high efficiency at light loads.The LTC3538 includes two 0.17Ω N-channel and two 0.2Ω P-channel MOSFET switches. Operating frequency is internally set to 1MHz to minimize solution footprint while maximizing efficiency.Other features include <5µA shutdown current, internal soft-start, short circuit protection and thermal shutdown. The LTC3538 is available in a low profile (0.75mm), thermally enhanced 8-lead (2mm x 3mm) DFN package.ApplicationsMiniature Hard Disk DrivesMP3 PlayersDigital CamerasCellular HandsetsPDAs, Handheld PCGPS Receivers

The LTC3539/LTC3539-2 are synchronous, 2A step-up DC/DC converters with output disconnect. Synchronous rectification enables high efficiency in the low profile 2mm × 3mm DFN package. Battery life is extended with a 700mV start-up voltage and operation down to 500mV once started.A switching frequency of 1MHz (LTC3539) or 2MHz (LTC3539-2) minimizes solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. The current mode PWM design is internally compensated, reducing external parts count. The LTC3539/LTC3539-2 feature a pin-enabled automatic Burst Mode operation at light load conditions. Anti-ring circuitry reduces EMI by damping the inductor in discontinuous mode. Additional features include a low shutdown current of under 1μA and thermal overload protection.The LTC3539/LTC3539-2 are offered in a 2mm × 3mm × 0.75mm DFN package.ApplicationsMedical InstrumentsPortable Bar Code ScannersNoise Canceling HeadphonesPortable GPS NavigationHandheld PCs

The LTC3541-2 combines a synchronous buck DC/DC converter with a very low dropout linear regulator (VLDO™regulator) and internal feedback resistor networks to provide two output voltages from a single input voltage with minimal external components. When configured for dual output operation, the LTC3541-2’s auto start-up feature will bring the 1.875V buck output into regulation in a controlled manner, prior to enabling the 1.5V VLDO output without the need for external pin control. The 1.5V VLDO/linear regulator output prior to 1.875V buck output sequencing may also be obtained via external pin control. The input voltage range is ideally suited for Li-Ion battery applications powering sub-3.3V logic from 5V or 3.3V rails.The synchronous buck converter provides a high efficiency output, typically 90%. It can provide up to 500mA of output current while switching at 2.25MHz, allowing the use of small surface mount inductors and capacitors. A mode select pin allows Burst Mode operation to be enabled for higher efficiency at light load currents, or disabled for lower noise, constant frequency operation.The VLDO regulator provides a low noise, low voltage output capable of providing up to 300mA of output current using only a 2.2μF ceramic capacitor. The input supply voltage of the VLDO regulator (LVIN) may come from the buck regulator output or a separate supply.OptionsVout Switcher (V)Vout VLDOAuto Start Up SequencingLTC3541Adj. down to 0.8VAdj. down to 0.4VSwitcher, then VLDOLTC3541-1Adj. down to 0.8VAdj down to 0.4VVLDO, then switcherLTC3541-21.875V fixed1.5V fixedSwitcher, then VLDOLTC3541-31.8V fixed1.575 fixedVLDO, then switcherApplicationsDigital CamerasCellular PhonesPC CardsWireless and DSL ModemsOther Portable Power Systems

The LTC3541-3 combines a synchronous buck DC/DC converter with a very low dropout linear regulator (VLDO™regulator) and internal feedback resistor networks to provide two output voltages from a single input voltage with minimum external components. When configured for dual output operation, the LTC3541-3’s auto start-up feature will bring the 1.575V VLDO/linear regulator output into regulation in a controlled manner prior to enabling the 1.8V buck output without the need for external pin control. The 300mA VLDO/linear regulator output will source only 30mA until the buck output achieves regulation. The input voltage range is ideally suited for applications powered from a Li-Ion battery and 5V or 3.3V rails.The synchronous buck converter provides a high efficiency output, typically 90%. It can provide up to 500mA of output current while switching at 2.25MHz, allowing the use of small surface mount inductors and capacitors. A mode select pin allows Burst Mode operation to be enabled for higher efficiency at light load currents, or disabled for lower noise, constant frequency operation.The VLDO regulator provides a low noise, low voltage output capable of providing up to 300mA of output current using only a 2.2μF ceramic capacitor. The input supply voltage of the VLDO regulator (LVIN) may come from the buck regulator or a separate supply.OptionsVout Switcher (V)Vout VLDOLTC3541Adj. down to 0.8VAdj. down to 0.4VLTC3541-1Adj. down to 0.8VAdj down to 0.4VLTC3541-21.875V fixed1.5V fixedLTC3541-31.8V fixed1.575 fixedApplicationsDigital CamerasCellular PhonesPC CardsWireless and DSL ModemsOther Portable Power Systems

The LTC3543 is a high efficiency monolithic synchronous current mode buck regulator.The switching frequency is internally set at 2.25MHz, allowing the use of small surface mount inductors and capacitors. In PLL mode, the LTC3543 can acquire frequencies between 1MHz and 3MHz. Also, the LTC3543 has spread spectrum capability providing a lower noise regulated output, as well as low noise at the input.In Burst Mode®operation, the supply current is only 45µA, dropping to <1µA in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3543 ideally suited for single Li-Ion battery-powered applications. The 100% duty cycle provides a low dropout operation, extending the battery life in portable systems. Burst Mode operation increases efficiency at light loads, further extending battery life. The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode.ApplicationsPortable InstrumentsCellular Phones

The LTC3544B is a quad, high efficiency, monolithic synchronous buck regulator using a constant frequency, current mode architecture. The four regulators operate independently with separate run pins. The 2.25V to 5.5V input voltage range makes the LTC3544B well suited for single Li-Ion/polymer battery-powered applications. 100% duty cycle provides low dropout operation, extending battery runtime in portable systems. At moderate and low output load levels PWM pulse skip mode operation provides very low output ripple voltage for noise sensitive applications.Switching frequency is internally set to 2.25MHz, allowing the use of small surface mount inductors and capacitors.The internal synchronous switches increase efficiency and eliminate the need for external Schottky diodes. Low output voltages are easily supported with the 0.8V feedback reference voltage.The LTC3544B is available in a low profile (0.75mm) (3mm × 3mm) QFN package.Light Load OperationLTC3544Burst Mode (20mVpp), < 70uA IqLTC3544BPulse Skip ModeApplicationsCellular TelephonesPersonal Information AppliancesWireless and DSL ModemsDigital Still CamerasMedia PlayersPortable Instruments