SP6682EU View Datasheet(PDF) - Signal Processing Technologies
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SP6682EU Datasheet PDF : 12 Pages
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APPLICATION INFORMATION: Continued
POWER EFFICIENCY
The efficiency of driving the white LEDs can
be calculated by:
� = VF • IF
Vi •Ii
=
Vi
•
(n
VF
• IF
•
+
IF
I Q)
� VF
Vi • n
Where Vi, Ii are input voltage and current VF,
IF are the forward voltage and operating
current of White LEDs; IQ is quiescent cur-
rent, which is considered small compared
with IF; n is the boost ratio (X1.5 or X2).
SP6682 HIGH VOLTAGE
WHITE LED DRIVER
The SP6682 can also be configured as a
high voltage boost converter to drive more
than 10 white LEDs. Figure 16 shows the
schematic of this application as well as
actual data showing efficiency of > 85%. By
using an external inductor, MOSFET and
diode, high output voltages can be
generated to drive 12 white LEDs (2
branches -- each branch has 6 white LEDs
in series). The current through the white
LEDs is determined by:
ILED
=
VFB
R1
Vin: 2.7-4.2V
C1
10uF
X5R Ceramic
EN/PWM
L1 LQH32CN4R7M11
4.7uH
DS SCHOTTKY MBR0530 ILED = VFB/R1 = 20mA
D1
D7
SP6682
1 VOUT
2 C1P
C2P 10
C1N 9
3 VIN
4 VMODE
5 FB
GND 8
C2N 7
EN/PWM 6
R3
1M
D2
D8
D3
D9
2.2uF 25V
C3 X5R
Q1
Ceramic
SI1304
D4
D10
SOT23
25V
D5
D11
D6
D12
R1
R2
15
15
Figure 16. Using SP6682 as a High Voltage White LED Driver
100
95
90
85
80
75
70
2.7 3.0 3.3 3.6 3.9 4.2
VIN (V)
PINOUTS
VOUT 1
C1P 2
VIN 3
VMODE 4
FB 5
10 C2P
SP6682
10 Pin DFN
9 C1N
8 GND
7 C2N
6 EN/PWM
VOUT 1
C1P 2
VIN 3
VMODE 4
FB 5
SP6682
10 Pin MSOP
10 C2P
9 C1N
8 GND
7 C2N
6 EN
Date: 7/19/06 Rev D
SP6682 High Efficiency Charge Pump Regulator for White LEDs
9
© 2006 Sipex Corporation
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