500mA, Synchronous Step-Down DC/DC Converter with Selectable Output Voltage

The LTC3563 is a high efficiency monolithic synchronous buck converter using a constant frequency, current mode architecture. A voltage select input allows the user to program the output voltage to 1.28V or 1.87V. Supply current during operation is only 26µA, dropping to <1µA in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3563 ideally suited for single Li-Ion battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Internal power switches are optimized to provide high efficiency and eliminate the need for an external Schottky diode.

The switching frequency is internally set at 2.25MHz, allowing the use of small surface mount inductors and capacitors. The LTC3563 is specifically designed to work well with ceramic output capacitors, achieving very low output voltage ripple and a small PCB footprint.

The LTC3563 is configured for the power saving Burst Mode Operation.

Applications

* Cellular Telephones

* Wireless and DSL Modems

* Digital Cameras

* MP3 Players

* PDAs and Other Handheld Devices

* High Efficiency: Up to 96%

* Pin Selectable Output Voltage: 1.28V/1.87V

* Low Ripple (<20mVP-P) Burst Mode® Operation: IQ = 26µA

* Very Low Quiescent Current: Only 26µA

* 2.5V to 5.5V Input Voltage Range

* 2.25MHz Constant Frequency Operation

* Low Dropout Operation: 100% Duty Cycle

* No Schottky Diode Required

* Internal Soft-Start Limits Inrush Current

* Shutdown Mode Draws <1µA Supply Current

* ±2% Output Voltage Accuracy

* Current Mode Operation for Excellent Line and Load Transient Response

* Overtemperature Protected

* Available in 2mm × 2mm 6-Lead DFN