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Synchronous Step-Down DC/DC Converter Delivers up to 500mA with Pin Selectable 1.28V/1.87 Outputs

9th October 2007

ES Admin

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Linear Technology has announced the LTC3563, a high efficiency, 2.25 MHz, synchronous buck regulator that can deliver up to 500mA of continuous output current from a 2mm x 2mm DFN package. Its output voltage is pin-selectable to either 1.28V or 1.87V, making it ideal for the latest generation of Agere cellphone baseband chipsets. Using a constant frequency and current mode architecture, the LTC3563 operates from an input voltage range of 2.5V to 5.5V, compatible with single cell Li-Ion, or multi-cell alkaline/NiCad/NiMH applications. Its 2.25MHz switching frequency enables the utilization of tiny, low cost ceramic capacitors and inductors less than 1mm in height, providing a very compact solution footprint for handheld applications.

The LTC3563 uses internal switches with an RDS(ON) of only 0.35 Ohm (N-Channel) and 0.50 Ohm (P-Channel) to deliver efficiencies as high as 96%. It also utilizes low dropout 100% duty cycle operation to allow output voltages equal to VIN, further extending battery run time. The LTC3563 utilizes low ripple (<20mVPK-PK) Burst Mode® operation, drawing only 26uA of no load quiescent current. Shutdown current is less than 1uA further maximizing battery run time. Other features include ±2% output voltage accuracy, internal soft-start and over-temperature protection.

The LTC3563EDC is available in a 2mm x 2mm DFN-6 package and is available from stock. Pricing starts at $1.60 each in 1,000-piece quantities.
Summary of Features of the LTC3563:

* Pin-Selectable Output Voltage: 1.28V/1.87V
* Low Ripple (<20mVp-p) Burst Mode Operation: IQ = 26uA
* 2.5V to 5.5V Input Voltage Range
* High Efficiency: Up to 96%
* 2.25MHz Constant Frequency Operation
* Low Dropout Operation: 100% Duty Cycle

· No Schottky Diode Required

* Internal Soft-Start Limits Inrush Current
* Shutdown Mode Draws <1uA Supply Current
* Current Mode Operation for Excellent Line & Load Transient Response
* Overtemperature Protected

· Available in 2mm x 2mm 6-Lead DFN