SP6685_06 Datasheet, PDF (10/16 Pages) Sipex Corporation – 700mA Buck/Boost Charge Pump LED Driver

TYPICAL PERFORMANCE CHARACTERISTICS
Application Circuit = Figure 31, T_A = 25°C.
100
90
80
Flash 600mA
Flash 300mA
Torch 150mA
Flash 400mA
Flash 500mA
Efficiency
70
60
50
40
3.0
3.2
3.4
3.6
3.8
4.0
4.2
Vin (V)
Output Current
900
Flash 600mA Vf=4.34V
800
Flash 500mA Vf=4.13V
Flash 400mA Vf=3.93V
700
Flash 300mA Vf=3.72V
Torch 150mA Vf=3.33V
600
500
400
300
200
100
0
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)
Figure 29. Efficiency vs. VIN.
Figure 30. Output Current vs. VIN.
APPLICATION INFORMATION
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 V_f for a given forward current I_f. In practice, if the V_f of one
LED is higher than the others, it will consume a larger I_f, which will raise its temperature which
will then cause its V_f to reduce, correcting the imbalance. The overall current will be the sum
of the individual currents, for example I_total = 4*ILED.
Vin: 3.0-4.2V
1
Cin
10uF
CF
1uF
2
3
J2
SP6685
1 _Vin
VOUT ¹⁰
2 _C1
PGND ⁹
3 _C2
SGND ⁸
4 _FLASH
IFB ⁷
5 _EN
ISET ⁶
Jumper
SW2
R EN
10K
R SET
139K
Push ON
Cout
4.7 uF
D1
Sharp LED
GM5BW05340AC
R FB VFB = 50mV Torch150mA
0.33 Ohm
100mV Flash 300mA
Figure 31. MULTIPLE LED FLASH CIRCUIT.
Date: 7/6/06 Rev B
SP6685, 700mA Buck/BoostCharge Pump LED Driver
10
© 2006 Sipex Corporation