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PDF EL7900 Data sheet ( Hoja de datos )
| Número de pieza | EL7900 | |
| Descripción | Ambient Light Photo Detect IC | |
| Fabricantes | Intersil Corporation | |
| Logotipo |  |
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®
Data Sheet
February 6, 2007
EL7900
FN7377.5
Ambient Light Photo Detect IC
The EL7900 is a light-to-current optical sensor combining a
photodiode and a current amplifier on a single monolithic IC.
Output current is directly proportionate to the light intensity
on the photodiode. Its sensitivity is superior to that of a
phototransistor and exhibits little variation. Its spectral
sensitivity matches closely to the luminous efficiency and
linearity.
Housed in an ultra-compact surface mount clear plastic
package, this device is excellent for power saving control
function in cell phones, PDAs, and other handheld
applications.
Pinout
EL7900
(5 LD ODFN)
TOP VIEW
www.DataSheet4U.com
VCC
GND
EN
OUTPUT
NC
Features
• Monolithic IC containing photodiode and amplifier
• 1lux to 8,000lux range
• Converts light intensity to current
• 2.5V to 5.5V supply range
• Low supply current: 1µA
• Fast response time - <200µs
• Excellent output linearity of luminance
• Ultra-compact and light surface mount package
• Pb-free plus anneal available (RoHS compliant)
Applications
• Mobile phones
• Notebook PCs
• PDAs
• Video cameras
• Digital cameras
Ordering Information
PART NUMBER
(Note)
TAPE &
REEL
PACKAGE
(Pb-free)
PKG.
DWG. #
EL7900ILCZ
- 5 Ld ODFN
L5.2x2.1
EL7900ILCZ-T7
7” 5 Ld ODFN
L5.2x2.1
NOTE: Intersil Pb-free products employ special Pb-free material
sets; molding compounds/die attach materials and 100% matte tin
plate termination finish, which are RoHS compliant and compatible
with both SnPb and Pb-free soldering operations. Intersil Pb-free
products are MSL classified at Pb-free peak reflow temperatures that
meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2005-2007. All Rights Reserved.
All other trademarks mentioned are the property of their respective owners.
1 page  
EL7900
In order to have the linear relationship between the input
light and the output current and voltage, a proper resistor
value (i.e., gain) should be picked for a specific input light
range. The resistor value can be picked according to the
following equation:
RLOAD
=
(---V----S----U----P-----–-----0---.--3----V----)
60 μ A
×
---1---0----0---l--u----x----
LRANGE
(EQ. 3)
Here, VSUP is the supply voltage, and LRANGE is the
specific input light range for an application. For example, an
indoor light ranges typically from 0lux to 1,000lux. A resistor
value of 4.5kΩ for 3V supply voltage can be used. For a
small light range, a large resistor value should be used to
achieve better sensitivity; for a large light range, a small
resistor value should be used to prevent non-linear output
current and voltage.
Resistor Output RLOAD Selection
The resistor output, RLOAD, determines the voltage transfer
function of the device. The device converts light into current
then RLOAD converts the output current to an output voltage.
RLOAD can range from 10Ω to 10MΩ depending on the input
lux levels. The table below lists RLOAD values to maximize
output swing for typical lux range levels. A careful balance of
dynamic swing and fast response has to be considered
when choosing RLOAD. For faster response, choose a
smaller value RLOAD to shunt stray capacitances that may
slow down response time. For maximum dynamic range or
swing, choose a higher value RLOAD. Although finite, the
output impedance of the device is considerably large.
Hence, the light-to-current conversion deviation because of
resistor loading is infinitesimal. The recommended maximum
RLOAD is 10MΩ.
The output current must never exceed 6mA. When using
load resistances less than 800Ω, care must be taken when
lux go as high as 10,000lux because the output current rises
above 6mA before reaching the device’s output compliance.
The output compliance of the device is 300mV below the
supply. The output current stops ramping when the output
voltage reaches voltage compliance.
TABLE 1. VDD = 5V, MAXIMUM OUTPUT VOLTAGE = 4.7V
ILLUMINATION RANGE
(lux)
RLOAD
(kΩ)
CURRENT OUT
(µA)
0 to 10
783 0 to 6
0 to 200
39.2 0 to 120
0 to 500
15.7 0 to 300
0 to 1,000
7.8 0 to 600
0 to 10,000
0.78 0 to 6,000
Application Examples
The following examples present from fully automatic to fully
manual override implementations. These guidelines are
applicable to a wide variety of potential light control
applications. The EL7900 can be used to control the
brightness input of CCFL inverters. Likewise, it can interface
well with LED drivers. In each specific application, it is
important to recognize the target environment and its
ambient light conditions. The mechanical mounting of the
sensor, light aperture hole size and use of a light pipe or
bezel are critical in determining the response of the EL7900
for a given exposure of light.
The example in Figure 10 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 and to filter 50/60Hz room lighting.
For example, suppose 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:
R1
=
R2
×
⎛
⎝
--3----.-0----V----
0.25 V
–
1⎠⎞
=
11 × R2
(EQ. 4)
3V TO 5V
SUPPLY VOLTAGE
3V DC VOLTAGE
VDO
EL7900
EN OUT
GND
R2
110k
TO INVERTER BRIGHTNESS
INPUT OR LED DRIVER
CONTROLLER
R1
10k
C1
25µF
FIGURE 10. AUTOMATIC DIMMING SOLUTION
Next, the value of R2 can be calculated based on the
maximum output current coming from the EL7900 under the
application's maximum light exposure. Suppose the current
has been determined to be about 125µA. Thus, R2 can be
calculated approximately as follows:
R2
=
⎛
⎝
1--1--2-.--25---5-μ---V-A--⎠⎞
=
10 k Ω
(EQ. 5)
and
R1 = 11 × R2 = 110kΩ
(EQ. 6)
5 FN7377.5
February 6, 2007
5 Page | ||
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| PDF Descargar | [ Datasheet EL7900.PDF ] | |
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