Analog Devices Inc./Maxim Integrated

The LTC3545/LTC3545-1 are triple, high efficiency, monolithic synchronous buck regulators using a constant frequency, current mode architecture. The regulators operate independently with separate run pins. The 2.25V to 5.5V input voltage range makes the LTC3545/LTC3545-1 well suited for single Li-Ion battery-powered applications. Low ripple pulse skip mode or high efficiency Burst Mode operation is externally selectable. PWM pulse skip mode operation provides very low output ripple voltage while Burst Mode operation increases efficiency at low output loads.Switching frequency is internally set to 2.25MHz, or the switching frequency can be synchronized to an external 1MHz to 3MHz clock. Power good indicators easily allow power on sequencing between the three regulators.The internal synchronous switches increase efficiency and eliminate external Schottky diodes. Low output voltages are supported with the 0.6V feedback reference voltage.The LTC3545-1 replaces the SYNC/MODE function with a third PGOOD pin and forces Burst Mode operation.ApplicationsSmart PhonesWireless and DSL ModemsDigital Still CamerasPortable InstrumentsPoint of Load Regulation

The LTC3547 is a dual, 2.25MHz, constant-frequency, synchronous step-down DC/DC converter in a tiny 3mm × 2mm DFN package. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Low output voltages are supported with the 0.6V feedback reference voltage. Each regulator can supply 300mA continuous output current.The input voltage range is 2.5V to 5.5V, making it ideal for Li-Ion and USB powered applications. Supply current during operation is only 40µA and drops to < 1µA in shutdown. Automatic Burst Mode®operation increases efficiency at light loads, further extending battery life.An internally set 2.25MHz switching frequency allows the use of tiny surface mount inductors and capacitors. Internal soft-start reduces inrush current during startup. All outputs are internally compensated to work with ceramic capacitors. The LTC3547 is available in a low profile (0.75mm) 3mm × 2mm DFN package.The LTC3547is also available in a fixed output voltage configuration,eliminating the need for the external feedback networksApplicationsCellular TelephonesDigital Still CamerasWireless and DSL ModemsPDAs/Palmtop PCsPortable Media Players

The LTC3547B is a dual, 2.25MHz, constant-frequency, synchronous step-down DC/DC converter in a tiny 3mm × 2mm DFN package. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Low output voltages are supported with the 0.6V feedback reference voltage. Each regulator can supply 300mA continuous output current.The input voltage range is 2.5V to 5.5V, making it ideal for Li-Ion polymer and USB powered applications. Supply current is only 1µA in shutdown.An internally set 2.25MHz switching frequency allows the use of tiny surface mount inductors and capacitors. Internal soft-start reduces inrush current during start-up. All outputs are internally compensated to work with ceramic capacitors. The LTC3547B is available in a low profile (0.75mm) 3mm × 2mm DFN package. The LTC3547B is also available in a fixed output voltage configuration selected via internal resistor dividers.ApplicationsCellular TelephonesDigital Still CamerasWireless and DSL ModemsPortable Media PlayersPDAs/Palmtop PCs

The LTC3548 is a dual, constant frequency, synchronous step down DC/DC converter. Intended for low power applications, it operates from 2.5V to 5.5V input voltage range and has a constant 2.25MHz switching frequency, allowing the use of tiny, low cost capacitors and inductors with a profile ≤1mm. Each output voltage is adjustable from 0.6V to 5V. Internal synchronous 0.35Ω, 0.7A/1.2A power switches provide high efficiency without the need for external Schottky diodes.A user selectable mode input is provided to allow the user to trade-off noise ripple for low power efficiency. Burst Mode operation provides high efficiency at light loads, while Pulse-Skipping Mode provides low noise ripple at light loads.To further maximize battery runtime, the P-channel MOSFETs are turned on continuously in dropout (100% duty cycle), and both channels draw a total quiescent current of only 40μA. In shutdown, the device draws <1μA.FeaturesLTC3548AImproved Burst Mode, Improved ESD, 2 Adjustable OutputsLTC3548-2One Fixed 1.8V Output, 1 AdjustableLTC3548-1Fixed 1.8V and 1.575V OutputsLTC35482 Adjustable OutputsApplicationsPDAs/Palmtop PCsDigital CamerasCellular PhonesPortable Media PlayersPC CardsWireless and DSL Modems

The LTC3548A is a dual, constant frequency, synchronous step-down DC/DC converter. Intended for low power applications, it operates from a 2.5V to 5.5V input voltage range and has a constant 2.25MHz switching frequency, enabling the use of tiny, low cost capacitors and inductors 1mm or less in height. Each output voltage is adjustable from 0.6V to 5V. Internal synchronous 0.35Ω, 0.7A/1.2A power switches provide high efficiency without the need for external Schottky diodes.A user-selectable mode input is provided to allow the user to trade-off ripple noise for low power efficiency. Burst Mode®operation provides the highest efficiency at light loads, while pulse-skipping mode provides the lowest ripple noise at light loads.To further maximize battery life, the P-channel MOSFETs are turned on continuously in dropout (100% duty cycle), and both channels draw a total quiescent current of only 40μA. In shutdown, the device draws <1μA.FeaturesLTC3548AImproved Burst Mode, Improved ESD, 2 Adjustable OutputsLTC3548-2One Fixed 1.8V Output, 1 AdjustableLTC3548-1Fixed 1.8V and 1.575V OutputsLTC35482 Adjustable OutputsApplicationsPDAs/Palmtop PCsDigital CamerasCellular PhonesWireless and DSL Modems

The LTC3550 is a standalone linear charger with a 600mA monolithic synchronous buck converter. It is capable of charging a single-cell Li-Ion battery from both wall adapter and USB inputs. The charger automatically selects the appropriate power source for charging.Internal thermal feedback regulates the battery charge current to maintain a constant die temperature during high power operation or high ambient temperature conditions. The float voltage is fixed at 4.2V and the charge currents are programmed with external resistors. The LTC3550 terminates the charge cycle when the charge current drops below the programmed termination threshold after the final float voltage is reached. With power applied to both inputs, the LTC3550 can be put into shutdown mode reducing the DCIN supply current to 20μA, the USBIN supply current to 10μA, and the battery drain current to less than 2μA.The DC/DC converter switching frequency is internally set at 1.5MHz, allowing the use of small surface mount inductors and capacitors.VoutLTC3550AdjustableLTC3550-11.875VApplicationsCellular Telephones

The LTC3552-1 is a complete constant-current/constant-voltage linear charger and dual fixed output DC/DC converter for single cell lithium-ion batteries. Its DFN package and low external component count make the LTC3552-1 ideally suited for portable applications. Furthermore, the LTC3552-1 is designed to work within USB power specifications.No external sense resistor or external blocking diode are required due to the internal MOSFET architecture. The charge voltage is fixed at 4.2V and the charge current is programmed with a resistor. The charge cycle terminates when the charge current drops below the programmed termination threshold after the final float voltage is reached. When the input supply (wall adapter or USB supply) is removed, the LTC3552-1 enters a low current state dropping the battery drain current to less than 2μA. Thermal regulation maximizes charge rate without risk of overheating.The synchronous step-down switching regulators generate fixed output voltages of 1.8V and 1.575V. The switching frequency is set at 2.25MHz, allowing the use of small surface mount inductors and capacitors.VOUTLTC3552Adjustable (0.6V to 5V)LTC3552-11.8V & 1.575VApplicationsCellular Telephones, PDAs, MP3 PlayersBluetooth Applications