LTC3218 Datasheet, PDF (1/12 Pages) Linear Technology – 400mA Single Wire Camera LED Charge Pump

LTC3218
400mA Single Wire
Camera LED Charge Pump
FEATURES
■ _{Low Noise Constant-Frequency Operation}
■ _{Multi-Mode Operation: 1x or 2x Boost Mode}
■ _{Automatic Mode Switching}
■ _{High Output Current: 150mA (Continuous), 400mA}
(Pulsed) From Li-Ion/Polymer Input
■ _{2-Second Flash Current Timeout for LED Protection}
■ _{Automatic Soft-Start}
■ _{Output Disconnect}
■ _{No Inductors}
■ _{220mΩ Internal High Side Current Sense Resistor}
■ _{Single Resistor Programming Capability}
■ _{Tiny Application Circuit (3mm × 2mm DFN Package,}
All Components < 1mm High)
APPLICATIONS
■ _{LED Torch/Flash Supply for DSCs/Cellphones}
DESCRIPTION
The LTC^®3218 is a low-noise, high-current charge pump
DC/DC converter capable of driving high current LEDs at up
to 400mA from a 2.9V to 4.5V input. A low external parts
count (one flying capacitor, two programming resistors and
two bypass capacitors at V_IN and CPO) make the LTC3218
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. A built-in 2-second timer
protects the LED during flash mode.
Output current level is programmed by an external re-
sistor. LED current is regulated using an internal high
side 220mΩ sense resistor. Automatic mode switching
optimizes efficiency by monitoring the voltage across the
charge pump and switching modes only when dropout
is detected. The part is available in a low profile 3mm ×
2mm 10-lead DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 6411531.
TYPICAL APPLICATION
2.2µF
2.9V TO 4.5V
2.2µF
DISABLED _ENABLED
DISABLED _ENABLED
ENF ENT
I_LED
0 0 0 (SHUTDOWN)
0 1 100mA (TORCH)
1 0 290mA
1 1 390mA (FLASH)
CP
V_IN
CM
CPO
LTC3218
ENF
ENT
I_SETF
I_LED
GND
I_SETT
10.2k
1%
4.7µF
LED
AOT2015
3218 TA01
Efficiency vs V_IN
100
90
80
70
60
50
50mA
150mA
300mA
40
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
V_IN (V)
3218 TA01b
3218fa
1