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参数资料
| 型号： | SP6682EB |
| 厂商： | Exar Corporation |
| 文件页数： | 9/13页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP6682 |
| 标准包装： | 1 |
| 系列： | * |
S P 6 6 8 2
H i g h E f f i c i e n c y W h i t e L E D C h a r g e P u m p R e g u l a t o r
I 1 V ? V F 1
B RIGHTNESS M ATCHING
For white LEDs, the forward voltage drop is a
function of the operating current. However, for
a given current, the forward voltage drops do
not always match due to normal man-
ufacturing tolerances, thus causing uneven
brightness of the white LEDs.In Figure 15,
assume high-precision bias resistors were
used, the operating current ratio of two
different branches can be easily derived as
shown by:
= OUT
I 2 V OUT ? V F 2
where I 1 , I 2 are the operating current of the
white LEDs andV F1 ,V F2 are the forward volt-age
of the white LEDs.
Where V I , I I are input voltage and current V F ,
I F are the forward voltage and operating
current of White LEDs; I Q is quiescent current,
which is considered small compared with I F ; η
is the boost ratio (x1.5 or x2).
SP6682 H IGH V OLTAGE W HITE LED
D RIVER
The SP6682 can also be configured as a high
voltage boost converter to drive more than 10
white LEDs. Figures 18 and 19 show 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:
Since the brightness of the white LED is
proportional to the operating current, for
better brightness matching, a higher output
voltage could be used. This could be done by
I LED =
V FB
R 1
using a larger resistor, as shown in Figure 17.
R B2 is used to bias the operating current of the
white LED, R B1 is used to increase the output
voltage. Better bright-ness matching was
achieved at the cost of the power wasted on
the bias resistor.
Fig. 18: Using SP6682 as a High Voltage White LED Driver
Fig. 17: Increasing Brightness Matching
P OWER E FFICIENCY
The efficiency of driving the white LEDs can be
calculated by:
V I × ( η × ( I F + I Q ) )
η =
V F × I F
V I × I I
=
V F × I F
=
V F
V I × η
Fig. 19: Efficiency of SP6882
as a High Voltage White LED Driver
? 2009 Exar Corporation
9/13
Rev. 2.0.0
相关PDF资料 |
PDF描述 |
|---|---|
| SP6683UEB | EVAL BOARD FOR SP6683 |
| SP6685EB | EVAL BOARD FOR SP6685 |
| SP6686EB | EVAL BOARD FOR SP6686 |
| SP6699EB | EVAL BOARD FOR SP6699 |
| SP6887EB | EVAL BOARD FOR SP6887 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| SP6682ER | 制造商:Exar Corporation 功能描述:Driver, Other |
| SP6682ER/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:High Efficiency Charge Pump Regulator for White LEDs |
| SP6682ER-L | 功能描述:电荷泵 White LEDs RoHS:否 制造商:Maxim Integrated 功能:Inverting, Step Up 输出电压:- 1.5 V to - 5.5 V, 3 V to 11 V 输出电流:100 mA 电源电流:1 mA 最大工作温度:+ 70 C 封装 / 箱体:SOIC-8 Narrow 封装:Tube |
| SP6682ER-L/TR | 功能描述:电荷泵 High Efficiency for White LEDs RoHS:否 制造商:Maxim Integrated 功能:Inverting, Step Up 输出电压:- 1.5 V to - 5.5 V, 3 V to 11 V 输出电流:100 mA 电源电流:1 mA 最大工作温度:+ 70 C 封装 / 箱体:SOIC-8 Narrow 封装:Tube |
| SP6682EU | 制造商:Exar Corporation 功能描述:Driver, Other |
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