el7900 Intersil Corporation, el7900 Datasheet - Page 4

• Manufacturer Part Number: el7900
• Description: Ambient Light Photo Detect Ic
• Manufacturer: Intersil Corporation

Typical Performance Curves
Pin Descriptions
Block Diagram
PIN
1
2
3
4
5
ENABLE
Output
NAME
3
GND
VCC
EN
NC
Supply, 2.5V to 5.5V
Ground
Enable
No connect
Current output pin
1
2
GND
VCC
4
DESCRIPTION
5
5
4
3
2
1
0
0
OUTPUT
FIGURE 9. I
1k
2k
3k
EL7900
LUMINANCE (lux)
OUT
4k
vs LUMINANCE
5k
Application Information
Product Description
The EL7900 is a light-to-current optical sensor combining
photodiodes and current amplifiers on a single monolithic IC.
The photodiodes are temperature-compensated and their
spectrum resembles the human eye response. The output
current is directly proportional to the intensity of light falling
on the photodiodes. For 100 lux of input fluorescent light, the
EL7900 has an output current of 60µA.
The EL7900 is housed in an ultra-compact surface mount
clear plastic package.
Light-to-Current and Voltage Conversion
The EL7900 has a responsiveness that is directly
proportional to the intensity of light intercepted by the
photodiodes. Although the conversion rate varies depending
on the light sources (fluorescent light, incandescent light or
direct sunlight), in general for a fluorescent light, the light-to-
current conversion is:
Here, I
input light in lux.
For some applications, a load resistor is added between the
output and the ground as shown in Figure 1. The output
voltage can be expressed in the following equation:
Here, V
the load resistor added. The compliance of the EL7900's
output circuit may result in premature saturation of the
output current and voltage when an excessively large
R
below the supply voltage as listed in V
Electrical Specifications table on page 2.
I
V
OUT
6k
OUT
LOAD
FLUORESCENT
LIGHT SOURCE
7k
=
=
OUT
OUT
⎛
⎝
is used. The output compliance voltage is 300mV
I
------------------ -
100lux
8k
OUT
60μA
is the output current in µA, and L
is the output voltage and R
9k
×
⎞
⎠
R
×
LOAD
10k
L
INPUT
=
⎛
⎝
-------------------- -
100 lux
60μA
⎞
⎠
×
L
INPUT
O(MAX)
LOAD
×
INPUT
R
is the value of
of the
LOAD
August 1, 2007
is the
FN7377.6
(EQ. 1)
(EQ. 2)