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PDF LX1971 Data sheet ( Hoja de datos )
| Número de pieza | LX1971 | |
| Descripción | Wide Range Visible Light Sensor | |
| Fabricantes | Microsemi Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LX1971 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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INTEGRATED PRODUCTS
LX1971
Wide Range Visible Light Sensor
PRODUCTION DATA SHEET
DESCRIPTION
The LX1971 is a new technology light Photo current is first multiplied by an
sensor with spectral response that integrated high gain amplifier then the
emulates the human eye; it is pin to pin square root is taken of the product of the
compatible to Microsemi’s LX1970 amplifier and an internal reference current.
visible light sensor however with a wider Finally this is further multiplied converted
dynamic range.
to current and made available at two
This device is ideal for monitoring output pins; one a current source and the
ambient light for the control of artificial other a current sink.
lighting, operation of shades, LED These currents can easily be converted
signage and display, street lighting, to voltage by adding a single resistor at
automotive light sensors and control of either or both outputs. Voltage gain is
backlight dimming. It has a unique photo determined by the resistor value typically
diode arrangement (patents pending) with in the 5KΩ to 50KΩ range.
a peak response at 520nm while sharply With accurate internal gain amplifiers
attenuating both ultra violet and infrared and square root transfer function, design
wavelengths.
complexity and cost are greatly reduced.
The photo sensor is a PIN diode array The LX1971 is available in the Clear 8-
with an accurate and very repeatable pin MSOP package.
current output.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
KEY FEATURES
Approximate Human Eye
Spectral Response
Low IR Sensitivity
Highly Accurate &
Repeatable Output Current
vs. Light
Square root transfer function
Temperature Stable
Integrated High Gain Photo
Current Amplifiers
Complementary Current
Outputs
No Optical Filters Needed
BENIFITS
• Requires no wavelength
filters
• Insensitive to UV and IR
• More than 4 decades usable
light range
• Enables accurate lighting
control systems
VDD
4.7uF
LX1971
4.7uF
PRODUCT HIGHLIGHT
VDD
25K
SNK
SNK
VOUT
SRC
25K
GND
SRC
Ambient
Light
0.60V Typ
0.45V Typ
Copyright 2003
Rev. 1.0,2003-11-25
DataSheet4 U .com
PACKAGE ORDER INFO
TA (°C)
Plastic MSOP
DU 8-Pin
-40 to 85
LX1971IDU
Note: Available in Tape & Reel.
Append the letter “T” to the part number. (i.e. LX1971IDUT)
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
1 page  
www.DataSheet4U.com
INTEGRATED PRODUCTS
LX1971
Wide Range Visible Light Sensor
PRODUCTION DATA SHEET
APPLICATION EXAMPLES
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 LX1971 can be used for the control of artificial
lighting, operation of shades, LED signage and display,
street lighting, automotive light sensors and control of
backlight dimming.
We are assuming a high impedance input to the LED driver.
In Figure 2 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. The PWM input source could
of course be replaced with an equivalent DC voltage.
3.3V or 5V
In each specific application it is important to recognize
the need to correlate the sink and source current of the
LX1971 for the target environment and its ambient light
VDD
VSS SNK
N/C
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 LX1971 for a given
exposure of light.
3.3V or 5V
3.3V PWM
SRC
R1
40K R2
25K
LED driver
controller or
dimming controller
10µF input
VDD
VSS SNK N/C
SRC
3V
R1
R2
LED driver
controller or
dimming controller
C1
10µF
input
Figure 1
The example in figure one shows a fully automatic
lighting control solution with no user interaction. Choose
R1 and R2 values for any desired minimum brightness and
slope. Choose C1 to adjust response time. 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 represent the maximum. The first
step would be to determine the ratio of R1 and R2.
R1 = R2 [ 3.0V/0.25V –1] = 11 * R2
Next the value of R2 can be calculated based on the
maximum output source current coming from the LX1971
under the application’s maximum light exposure, lets say
this has been determined to be about 50uA . Thus R2 can
be calculated first order as follows:
R2 = [ 1.25V / 50uA ] = 25KΩ ∴ R1 = 11 * R2 = 275KΩ
The output node will actually reach 1.25V when the
source current from the LX1971 is only about 44uA since
about 6uA of current will be contributed from R1.
Figure 2
Figure 3 shows how a fully manual override can be quickly
added to the example in figure 2. In addition to the gate to turn
on and off the LX1971, a diode has been inserted to isolate the
LX1971 when it is shut down.
Diable
control
CMOS
Gate
VDD
VSS SNK
SRC
N/C
3.3V
PWM
60K
30K
10µF
LED driver
controller or
dimming controller
30K input
Figure 3
The preceding examples represent just a few of the many
ways the sensor can be used. For example since there is also a
complimentary sink output a resistor from VDD to SNK could
develop a voltage that could be compared (with some
hysteresis) to a fixed (or adjustable) reference voltage and
develop a logic signal. In the case of street lighting or
operation of shades such a signal would engage the function
when reaching the correct ambient light level.
Copyright 2003
Rev. 1.0,2003-11-25
DataSheet4 U .com
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet LX1971.PDF ] | |
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