Jul16-07 RevP

SP7686: 500mA LED Driver

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2007 Sipex Corporation

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PIN DESCRIPTION

PIN #

PIN

NAME

SP7686 PIN DESCRIPTION

1

Power supply input. Place a 10µF decoupling capacitor next to this pin.

2, 3

C1, C2

Connect an external 0.22µF flying capacitor between these pins

4

CTRL

This pin is used to control LED current. Once enabled the adjustable driver counts positive

going edges at this pin and sequentially increases FB voltage with 10mV steps to a

maximum 31 steps or 360mV.

When this pin is held LOW for longer than 200µs the

SP7686 enters shutdown. The part can be enabled using this pin. The first positive edge

resets the part. A second positive edge sets the part to VFB=0. A third positive going edge

will increase FB voltage to 60mV and subsequent positive edges increment VFB in 10mV

steps. The voltage level can increase only and must be reset to zero by the 200µs shutdown

timer in order to go to a lower current value. The part will be limited to a 3.5s on time when

FB voltage is set to 120mV and above. This pin cannot be left open.

5

FB

Current feedback input. Place an external current sense resistor from this pin to ground.

Voltage at this pin will be internally compared to the DAC output (60mV – 360mV).

6

SGND

Ground pin for SP7686 bias and reference (low current).

7

PGND

Ground pin for power (high current).

8

Output voltage of the internal charge pump. Connect the LED between this pin and the

current sense resistor. Voltage at this pin will be regulated in order to maintain constant LED

current. Place a 2.2µF ceramic capacitor next to this pin.

PIN #

PIN

NAME

SP7686A PIN DESCRIPTION

1

Power supply input. Place a 10µF decoupling capacitor next to this pin.

2, 3

C1, C2

Connect an external 0.22µF flying capacitor between these pins

4

FLASH

The fixed current driver (SP7686A) uses the flash pin to switch between two internally

preset voltage levels, for Flash and Torch mode. The part is enabled and disabled by the

separate ENABLE pin. The part has a 3.5s maximum on time in Flash mode. After a 3.5s

timeout occurs the part shuts down and can be enabled by the FLASH or ENABLE pins.

This pin cannot be left open.

5

FB

Current feedback input. Place an external current sense resistor from this pin to ground.

Voltage at this pin will be internally compared to the DAC output (60mV – 360mV).

6

EN

The fixed current driver (SP7686A) has this enable/shutdown pin. (Logic high = enable, logic

low = shutdown). Used to immediately disable the driver and PWM brightness control. There

is an internal pull down on this pin.

7

PGND

Ground pin for power (high current).

8

Output voltage of the internal charge pump. Connect the LED between this pin and the

current sense resistor. Voltage at this pin will be regulated in order to maintain constant LED

current. Place a 2.2µF ceramic capacitor next to this pin.