Datasheet LTC3447 (Analog Devices)

LTC3447 I2C Controllable Buck Regulator in 3mm × 3mm DFN
U FEATURES DESCRIPTIO
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I2C Programmable Output with 21.6mV Resolution
The LTC®3447 is a high effi ciency monolithic synchronous ■
Overtemperature Protected
current mode buck regulator. Using an I2C interface, the ■
High Effi ciency: Up to 93%
output voltage can be set between 0.69V and 2.05V using ■
Very Low Quiescent Current: Only 33µA
an internal 6-bit DAC. ■
600mA Output Current at VIN = 3V
The buck regulator has optional external feedback resis- ■ 2.5V to 5.5V Input Voltage Range tors that can be used for setting the initial start up voltage. ■ 1MHz Constant Frequency Operation The feedback voltage reference for this start-up option ■ No Schottky Diode Required is 0.6V. Once the voltage DAC is updated via the I2C, the ■ Low Dropout Operation: 100% Duty Cycle buck regulator switches from external to internal feedback ■ Stable with Ceramic Capacitors resistors. When there are no external resistors, the default ■ Shutdown Mode Draws <1µA Supply Current start-up voltage is 1.38V. ■ ±2% Output Voltage Accuracy ■ Standard (100kHz) or Fast Mode (400kHz) I2C The switching frequency is internally set at 1MHz, al- ■ 6-Bit Voltage DAC (0.69V to 2.05V) lowing the use of small surface mount inductors and ■ Disable Burst Mode Operation capacitors. ■ Enable Power Good Blanking In Burst Mode® operation, supply current is only 33µA, ■ Optional External Start-Up Resistors dropping to <1µA in shutdown. The 2.5V to 5.5V input ■ Soft-Start voltage range makes the LTC3447 ideally suited for single ■ 10 Lead, 3mm × 3mm DFN Package cell Li-Ion battery-powered applications. 100% duty cycle
U
capability provides low dropout operation, extending
APPLICATIO S
battery life in portable systems. Automatic Burst Mode ■ Distributed Power Supplies operation increases effi ciency at light loads, further ex- ■ Notebook Computers tending battery life. ■ PDAs and Other Handheld Devices The internal synchronous switch increases effi ciency and , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. eliminates the need for an external Schottky diode. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131.
U TYPICAL APPLICATIO Effi ciency and Power Loss vs Load Current (VIN = 3.6V)
VIN 100 1000 2.5V TO 5.5V C2 4.7µF VIN 90 CERAMIC RPU1 80 20k POWER LOSS (mW) VIN 70 100 PWREN RUN PGOOD I2C VCCD VOUT 60 LTC3447 0.69V VCCD SW TO 2.05V 50 C3 L1 C1 AT 600mA* 10k 10k 4.7µF 3.3µH 40 SDA V 10µF R1 OUT EFFICIENCY (%) 100k 10 SDA 30 SCL FB SCL 20 PULSE SKIP EFFICIENCY R2 GND 10 Burst Mode EFFICIENCY 49.9k LOSS * 600mA AT VIN = 3V 0 1 EXPOSED PADDLE 1 10 100 1000 TO GROUND 3447 TA01 LOAD CURRENT (mA) 3447 TA01b 3447f 1