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LTC3447 - I²C Controllable Buck Regulator in 3mm × 3mm DFN

The buck regulator has optional external feedback resis-tors that can be used for setting the initial start up voltage. The feedback voltage reference for this start-up option is 0.6V. Once the voltage DAC is updated via the I2C, the buck regulator switches from external to internal feedback resistors. When there are no external resistors, the default start-up voltage is 1.38V.

The switching frequency is internally set at 1MHz, allowing the use of small surface mount inductors and capacitors.

In Burst Mode® operation, supply current is only 33µA, dropping to <1µA in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3447 ideally suited for single cell Li-Ion battery-powered applications. 100% duty cycle capability provides low dropout operation, extending battery life in portable systems. Automatic Burst Mode operation increases efficiency at light loads, further extending battery life.

The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode.

Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131.

Features I2C Programmable Output with 21.6mV Resolution Overtemperature Protected High Efficiency: Up to 93% Very Low Quiescent Current: Only 33µA 600mA Output Current at VIN = 3V 2.5V to 5.5V Input Voltage Range 1MHz Constant Frequency Operation No Schottky Diode Required Low Dropout Operation: 100% Duty Cycle Stable with Ceramic Capacitors Shutdown Mode Draws <1µA Supply Current ±2% Output Voltage Accuracy Standard (100kHz) or Fast Mode (400kHz) I2C 6-Bit Voltage DAC (0.69V to 2.05V) Disable Burst Mode Operation Enable Power Good Blanking Optional External Start-Up Resistors Soft-Start 10 Lead, 3mm × 3mm DFN Package Typical Application

Applications Distributed Power Supplies Notebook Computers PDAs and Other Handheld Devices Packaging

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