High Efficiency, Low Noise, Inductorless Step-Down DC/DC Converter

The LTC3250-1.5/LTC3250-1.2 are charge pump step-down DC/DC converters that produce a 1.5V or 1.2V regulated output from a 2.7V to 5.5V input. The parts use switched capacitor fractional conversion to achieve typical efficiency two times higher than that of a linear regulator. No inductors are required.

A unique constant frequency architecture provides a low noise regulated output as well as lower input noise than conventional charge pump regulators.* High frequency operation (fOSC = 1.5MHz) simplifies filtering to further reduce conducted noise. The part also uses Burst Mode® operation to improve efficiency at light loads.

Low operating current (35µA with no load, <1µA in shutdown) and low external parts count (three small ceramic capacitors) make the LTC3250-1.5/LTC3250-1.2 ideally suited for space constrained battery powered applications. The parts are short-circuit and over-temperature protected, and are available in a low profile (1mm) 6-pin ThinSOT™ package.

*U.S. Patent #6, 411, 531

Applications

* Handheld Computers

* Cellular Phones

* Digital Cameras

* Handheld Medical Instruments

* Low Power DSP Supplies

* 2.7V to 5.5V Input Voltage Range

* No Inductors

* Li-Ion (3.6V) to 1.5V with 81% Efficiency

* Low Noise Constant Frequency Operation

* Output Voltages: 1.5V ±4%, 1.2V ±4%

* Output Current: 250mA

* Shutdown Disconnects Load from VIN

* Low Operating Current: IQ = 35µA

* Low Shutdown Current: ISD <1µA

* Oscillator Frequency = 1.5MHz

* Soft-Start Limits Inrush Current at Turn-On

* Short-Circuit and Overtemperature Protected

* Low Profile (1mm) ThinSOT Package