LTC3215 Datasheet, PDF (1/12 Pages) Linear Technology – 700mA Low Noise High Current LED Charge Pump

FEATURES
■ _{High Efficiency Operation: 1x, 1.5x or 2x Boost}
Modes with Automatic Mode Switching
■ _{Ultralow Dropout ILED Current Control}
■ _{Output Current up to 700mA}
■ _{Low Noise Constant Frequency Operation*}
■ _{Wide VIN Range: 2.9V to 4.4V}
■ _{Open/Shorted LED Protection}
■ _{LED Disconnect in Shutdown}
■ _{Low Shutdown Current: 2.5µA}
■ _{4% LED Current Programming Accuracy}
■ _{Automatic Soft-Start Limits Inrush Current}
■ _{No Inductors}
■ _{Tiny Application Circuit (All Components <1mm}
Profile)
■ _{3mm × 3mm 10-Lead DFN Package}
U
APPLICATIO S
■ _{LED Torch/Camera Light Supply for Cell Phones,}
PDAs and Digital Cameras
■ _{General Lighting and/or Flash/Strobe Applications}
LTC3215
700mA Low Noise High
Current LED Charge Pump
DESCRIPTIO
The LTC^®3215 is a low noise, high current charge pump
DC/DC converter designed to power high current LEDs.
The part includes an accurate programmable current
source capable of driving loads up to 700mA from a 2.9V
to 4.4V input. Low external parts count (two flying capaci-
tors, one programming resistor and two bypass capaci-
tors) makes the LTC3215 ideally suited for small, battery-
powered applications.
Built-in soft-start circuitry prevents excessive inrush cur-
rent during start-up. High switching frequency enables the
use of small external capacitors. LED current is pro-
grammed with an external resistor. The LED is discon-
nected from V_IN during shutdown.
An ultralow dropout current source maintains accurate
LED current at very low I_LED voltages. Automatic mode
switching optimizes efficiency by monitoring the voltage
across the LED current source and switching modes only
when I_LED dropout is detected. The LTC3215 is available in
a low profile 3mm × 3mm 10-Lead DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*Protected by U.S. Patent 6411531.
TYPICAL APPLICATIO
C1
2.2µF
C2
2.2µF
2.9V TO 4.4V
C_IN
2.2µF
DISABLE ENABLE
C1⁺ C1^– C2⁺ C2^–
V_IN
CPO
LTC3215
I_LED
EN
I_SET
20k
1%
3215 TA01a
LED1: AOT2015 HPW 1751B
LED1
I_LED
200mA
C_CPO
4.7µF
Efficiency vs V_IN
100
90
I_LED = 200mA
80
70
60
50
40
30
20
10 ^{LED = AOT2015 HPW 1751B}
V_F = 3V TYP AT 200mA
0
2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4
V_IN (V)
3215 TA01b
3215f
1