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參數資料
| 型號： | LX1974IBC |
| 廠商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分類： | 光電元器件 |
| 英文描述： | Ambient Light Detector |
| 中文描述： | LOGIC OUTPUT PHOTO DETECTOR |
| 封裝： | ROHS COMPLIANT, PLASTIC, 1206, 2 PIN |
| 文件頁數： | 6/9頁 |
| 文件大?。?/td> | 352K |
| 代理商： | LX1974IBC |
LX1974
P
RODUCTION
D
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S
HEET
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
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Ambient Light Detector
Copyright
2005
Rev. 1.0, 2006-05-09
TM
A P P L I C A T I O N E X A M P L E S
The following examples present both fully automatic
(no user input) and semi-automatic to fully manual
override implementations. These general guidelines are
applicable to a wide variety of potential light control
applications. The LX1974 can be used to control the
brightness input of CCFL inverters (like Microsemi’s
PanelMatch inverter family, or line of controller IC’s).
Likewise, it can interface well with LED drivers like the
LX1990 and LX1991 sink LED drivers, or boost drivers
like the LX1992, LX1993, LX1994, and LX1995.
In each specific application, it is important to recognize
the need to correlate the output current of the LX1974 for
the target environment and its ambient light conditions.
The mechanical mounting of the sensor, light aperture
hole size, use of a light pipe or bezel are critical in
determining the response of the LX1974 for a given
exposure of light.
R1
R2
C1
10μF
3V
To inverter brightness
input or LED driver
controller.
3.3V or 5V
VSS
VDD
Figure 4 –
Fully Automatic Dimming
The example in figure 4 shows a fully automatic
dimming solution with no user interaction. Choose R1
and R2 values for any desired minimum brightness and
slope. Choose C1 to adjust response time to filter 50/60
Hz room lighting. As an example, let’s say you wish to
generate an output voltage from 0.25V to 1.25V to drive
the input of an LED driver controller. The 0.25V
represents the minimum LED brightness and 1.25V
represents the maximum. The first step would be to
determine the ratio of R1 and R2.
R2
11
1
0.25V
3.0V
R2
R1
×
=
=
Next the value of R2 can be calculated based on the
maximum output source current coming from the
LX1974 under the application’s maximum light exposure,
lets say this has been determined to be about 50μA .
Thus R2 can be calculated; first order as follows:
1.25V
R2
∴
=
=
275K
R2
11
R1
25K
50μA
=
×
=
The output node will actually reach 1.25V when the source
current from the LX1974 is only about 44μA since about
6μA of current will be contributed from R1. This assumes a
high impedance input to the LED driver. In Figure 5, user
adjustable bias control has been added to allow control over
the minimum and maximum output voltage. This allows the
user to adjust the output brightness to personal preference
over a limited range. In addition, an equivalent DC voltage
may replace the PWM input source.
R1
40K
R2
25K
10μF
To inverter
brightness input or
LED driver
controller input.
3.3V or 5V
VSS
VDD
3.3V PWM
Figure 5 –
Semi-Manual Controlled Dimming
Figure 6 shows how a fully manual override can be quickly
added to the example in figure 5. In addition to the gate to
turn on and off the LX1974, a diode has been inserted to
isolate the sensor when it is disabled.
30K
30K
10μF
To inverter
brightness input or
LED driver
controller.
VSS
VDD
PWM
CMOS
Gate
60K
3.3V
Disable
control
Figure 6 –
Fully Manual Controlled Dimming
The preceding examples represent just a few of the
potential sensor applications. Further details and additional
circuits can be found in the application note (AN-28) LX1970
Visible Light Sensor located in the application section of
Microsemi’s website:
www.microsemi.com
. Although this
application note is written around the LX1970 visible light
sensor the circuits can be easily adapted for use with the
LX1974.
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相關代理商/技術參數 |
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| LX1977 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SMBus Ambient Light Sensor |
| LX1977 EVAL KIT | 制造商:Microsemi Corporation 功能描述:VISIBLE LIGHT SENSOR - Bulk |
| LX1977IDU | 制造商:Microsemi Corporation 功能描述:VISIBLE LIGHT SENSOR - Bulk |
| LX1977IDU-TR | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SMBus Ambient Light Sensor |
| LX1990 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:Dual Programmable LED Current Sink |
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