SP6685 datasheet(10/16 Pages) SIPEX

10 / 16 page

Date: 7/6/06 Rev B

SP6685, 700mA Buck/BoostCharge Pump LED Driver

TYPICAL PERFORMANCE CHARACTERISTICS

The SP6685 can be used with multiple LEDs in parallel as shown in figure 31. For best

performance, the LEDs should be in a single package, preferably from a single die to have

better matching for forward voltage Vf for a given forward current If. In practice, if the Vf of one

LED is higher than the others, it will consume a larger If, which will raise its temperature which

will then cause its Vf to reduce, correcting the imbalance. The overall current will be the sum

of the individual currents, for example Itotal = 4*ILED.

GM5BW05340AC

Sharp LED

Cout

4.7 uF

1uF

Vin: 3.0-4.2V

SP6685

Vin

IFB

ISET

FLASH

SGND

PGND

VOUT

R SET

139K

R EN

10K

Cin

10uF

R FB

0.33 Ohm

SW2

Push ON

VFB = 50mV Torch150mA

100mV Flash 300mA

Jumper

Efficiency

100

3.0

3.2

3.4

3.6

3.8

4.0

4.2

Vin (V)

Flash 600mA

Flash 300mA

Torch 150mA

Flash 400mA

Flash 500mA

Output Current

100

200

300

400

500

600

700

800

900

3.0

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

4.0

4.1

4.2

Vin (V)

Flash 600mA Vf=4.34V

Flash 500mA Vf=4.13V

Flash 400mA Vf=3.93V

Flash 300mA Vf=3.72V

Torch 150mA Vf=3.33V

Figure 29. Efficiency vs. VIN.

Figure 30. Output Current vs. VIN.

Figure 31. MULTIPLE LED FLASH CIRCUIT.

APPLICATION INFORMATION

Application Circuit = Figure 31, TA = 25°C.

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