500mA High Efficiency, Low Noise, Inductorless Step-Down DC/DC Converters

The LTC3251/LTC3251-1.2/LTC3251-1.5 are 2-phase charge pump step-down DC/DC converters that produce a regulated output from a 2.7V to 5.5V input. The parts use switched capacitor fractional conversion to achieve twice the typical efficiency of a linear regulator. No inductors are required. VOUT is resistor programmable from 0.9V to 1.6V or fixed at 1.2V or 1.5V, with up to 500mA of load current available.

A unique 2-phase spread spectrum architecture provides a very low noise regulated output as well as low noise at the input. The parts have four operating modes: Continuous Spread Spectrum, Spread Spectrum with Burst Mode operation, Super Burst™ mode operation and shutdown.

Low operating current (35µA in Burst Mode operation, 10µA in Super Burst mode operation) and low external parts count make the LTC3251/LTC3251-1.2/LTC3251-1.5 ideally suited for space-constrained battery-powered applications. The parts are short-circuit and over-temperature protected, and are available in a thermally enhanced 10-pin MSOP package.

Applications

* Handheld Devices

* Cellular Phones

* Portable Electronic Equipment

* DSP Power Supplies

* Up to 500mA Output Current

* No Inductors

* 2.7V to 5.5V Input Voltage Range

* 2x Efficiency Improvement Over LDOs

* 2-Phase, Spread Spectrum Operation for Low Input and Output Noise

* Shutdown Disconnects Load from VIN

* Adjustable Output Voltage Range: 0.9V to 1.6V

* Fixed Output Voltages: 1.2V, 1.5V

* Super Burst, Burst and Burst Defeat Operating Modes

* Low Operating Current: IIN = 35µA (Burst Mode® Operation)

* Super Burst Operating Current: IIN = 10µA

* Low Shutdown Current: IIN = 0.01µA Typ

* Soft-Start Limits Inrush Current at Turn-On

* Short-Circuit and Overtemperature Protected

* Available in a Thermally Enhanced 10-Pin MSOP Package