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参数资料
| 型号： | SP6683UEB |
| 厂商： | Exar Corporation |
| 文件页数： | 11/14页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP6683 |
| 标准包装： | 1 |
| 系列： | * |
APPLICATION INFORMATION
Brightness Matching
For white LEDs, the forward voltage drop is a
function of the operating current. However, for
a given current, the forward voltage drop across
each LED does not always match exactly. This
can cause uneven brightness in the white LEDs.
In the figure below, assuming high-precision
bias resistors were used, the operating current
ratio of two different branches can be easily
derived as shown by:
used. This could be done by using a larger
resistor, as shown in the figure below. Rb2 is
used to bias the operating current of the white
LED, Rb1 is use to increase the output voltage.
Better brightness matching was achieved at the
cost of the power wasted on the bias resistor.
Power Efficiency
The efficiency of driving the white LEDs can be
I 1
V OUT - V F1
=
I 2 V OUT - V F2
where I 1 & I 2 are the operating current of the
white LEDs, where V F1 & V F2 are the forward
voltage of the white LEDs.
calculated by
η = V F ? I F =
V i ? I i
Where
V F ? I F
V i ? (n ? I F + I Q )
≈
V F
V i ? n
V i & I i are input voltage and current;
Since the brightness of the white LED is propor-
tional to the operating current, for better bright-
ness matching, a higher output voltage could be
V F & I F are the forward voltage and operating
current of the White LED;
I Q is quiescent current, which is considered
small compared with I F .
V OUT
1
I 1
I 2
D1
VF1
D2
VF2
I n
Dn
VFn
SP6683
Rb1
GND
8
V FB
5
Rb2
Rb
Rb
Rb
Improving brightness matching
Date: 3/31/06 RevG
SP6683 1X/1.5X Charge Pump LED Driver for Flash or Backlight
11
? Copyright 2006 Sipex Corporation
相关PDF资料 |
PDF描述 |
|---|---|
| SP6685EB | EVAL BOARD FOR SP6685 |
| SP6686EB | EVAL BOARD FOR SP6686 |
| SP6699EB | EVAL BOARD FOR SP6699 |
| SP6887EB | EVAL BOARD FOR SP6887 |
| SP7121EB | EVAL BOARD FOR SP7121 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| SP6685 | 制造商:EXAR 制造商全称:EXAR 功能描述:700mA Buck/Boost Charge Pump LED Driver |
| SP6685_06 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:700mA Buck/Boost Charge Pump LED Driver |
| SP6685EB | 功能描述:电源管理IC开发工具 Eval Board for SP6685 Series RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| SP6685ER | 制造商:Exar Corporation 功能描述:LASER DIODE/LED DRIVER, 10 Pin, Plastic, LCC |
| SP6685ER/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:700mA Buck/Boost Charge Pump LED Driver |
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