LTC3217
600mA Low Noise
Multi-LED Camera Light
Charge Pump
DESCRIPTIO
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FEATURES
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Charge Pump Provides High Efficiency with
Automatic Mode Switching
Multimode Operation: 1x, 1.5x, 2x
Four Low Dropout LED Outputs
Up to 600mA Total Output Current
Independent Torch and Flash ISET and Enable Pins
Low Noise Constant Frequency Operation*
PWM Brightness Control via the EN2 Pin
Low Shutdown Current: 4µA
Internal Soft-Start Limits Inrush Current During
Start-Up and Mode Switching
Open/Short LED Protection
No Inductors
(3mm x 3mm) 16-Lead QFN Plastic Package
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APPLICATIO S
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The LTC®3217 is a low noise charge pump DC/DC converter designed to power four high current LEDs. The
LTC3217 requires only four small ceramic capacitors and
two current set resistors to form a complete LED power
supply and current controller.
Built-in soft-start circuitry prevents excessive inrush current during start-up and mode changes. High switching
frequency enables the use of small external capacitors.
Independent high and low current settings are programmed
by two external resistors. Shutdown mode and current
output levels are selected via two logic inputs.
The current through the LEDs is programmed via ISET1 and
ISET2. In addition, the brightness can be controlled by
pulse width modulation of the EN2 pin.
The charge pump optimizes efficiency based on the voltage across the LED current sources. The part powers up
in 1x mode and will automatically switch to boost mode
whenever any enabled LED current source begins to enter
dropout. The first dropout switches the part into 1.5x
mode and a subsequent dropout switches the part into 2x
mode. The LTC3217 resets to 1x mode whenever the part
is shut down.
Multi-LED Camera Light Supply for Cellphones/
DSCs/PDAs
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. Patents, including 6411531
The LTC3217 is available in a low profile 16-lead (3mm ×
3mm × 0.75mm) QFN package.
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TYPICAL APPLICATIO
C2
2.2µF
Efficiency vs VBAT
C3
2.2µF
100
90
VBAT
C1M C2P
C2M
VBAT
C1
2.2µF
CPO
C4
2.2µF
LTC3217
AOT-2015HPW-1751B
LED1
LED2
EN1 (TORCH)
EN1
LED3
EN2 (FLASH)
EN2
LED4
ISET1
19.6k
1%
ISET2
GND
6.49k
1%
EN1
0
1
0
1
EN2
0
0
1
1
ILED
0 (SHUTDOWN)
25mA/LED
75mA/LED
100mA/LED
EFFICIENCY (PLED/PIN) (%)
C1P
100mA 200mA
400mA
80
70
60
50
40
30
20
TOTAL OUTPUT CURRENT
PLED/PIN
LED = 2015 HPW AOT
10
0
3
3217 TA01
3.2
3.4
3.6 3.8
VBAT (V)
4
4.2
4.4
3217 G09
3217f
1
