LTC3217

1

3217f

FEATURES

DESCRIPTIO

DSCs/PDAs

Automatic Mode Switching

µA

Start-Up and Mode Switching

600mA Low Noise

Multi-LED Camera Light

Charge Pump

The LTC

verter 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 cur-

rent 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.

pulse width modulation of the EN2 pin.

The charge pump optimizes efficiency based on the volt-

age 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.

The LTC3217 is available in a low profile 16-lead (3mm

×

3mm

× 0.75mm) QFN package.

TYPICAL APPLICATIO

APPLICATIO S

C2

2.2

µF

C3

2.2

µF

C1

2.2

µF

19.6k

1%

6.49k

1%

LED1

LED2

LED3

LED4

GND

EN2

EN1

LTC3217

C1P

C1M C2P

C2M

C4

2.2

µF

AOT-2015HPW-1751B

3217 TA01

CPO

EN1 (TORCH)

EN2 (FLASH)

EN1

0

1

0

1

0 (SHUTDOWN)

25mA/LED

75mA/LED

100mA/LED

EN2

0

0

1

1

, 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

3

0

10

30

40

50

100

70

3.4

3.8

4

3217 G09

20

80

90

60

3.2

3.6

4.2

4.4

TOTAL OUTPUT CURRENT

LED = 2015 HPW AOT

100mA

200mA

400mA