1
®
FN7377.8
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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EL7900
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 exhib its little variati on. 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
Features
• Monolithic IC containing photodiode and amplifier
• 1lux to 8,000lux range
• Converts light intensity to current
• 2.7V 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 (RoHS compliant)
Applications
• Mobile phones
• Notebook PCs
•PDAs
• Video cameras
• Digital cameras
1
2
3
5
4
VCC
GND
EN
OUTPUT
NC
THERMAL
PAD
Ordering Information
PART NUMBER
(Note) TEMP RANGE
(°C) PACKAGE
(Pb-Free) PKG.
DWG. #
EL7900ILCZ -40 to +85 5 Ld ODFN L5.2x2.1
EL7900ILCZ-T7* -40 to +85 5 Ld ODFN
Tape and Reel L5.2x2.1
EL7900ILCZ-EVALZ Evaluation Board
*Please refer to TB347 for details on reel specifications.
NOTE: These Intersil Pb-free plastic packaged products employ
special Pb-free material sets; molding compounds/die attach
materials and 100% matte tin plate - e3 termination finish, which is
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.
Data Sheet September 18, 2009
2FN7377.8
September 18, 2009
Absolute Maximum Ratings (TA = +25°C) Thermal Information
Supply Voltage between VSD and GND . . . . . . . . . . . . . . . . . . . .6V
Maximum Continuous Output Current . . . . . . . . . . . . . . . . . . . . 6mA
ESD Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV
Operating Conditions
Temperature Range. . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
Thermal resistance (Typical, Note 1) θJA (°C/W)
ODFN Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
Maximum Die Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . .+90°C
Storage Temperature. . . . . . . . . . . . . . . . . . . . . . . .-40°C to +100°C
Pb-free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and
result in failures not covered by warranty.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
NOTE:
1. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
Tech Brief TB379
Electrical Specifications VCC = 3V, TA = +25°C, unless otherwise specified.
PARAMETER DESCRIPTION CONDITION MIN TYP MAX UNIT
VDD Power Supply Range 2.7 5.5 V
ICC1 Supply Current RL = 1kΩ, EV = 100lux 68 µA
EV = 0lux 1 µA
ICC2 Supply Current When Disabled EN = VHI 0.5 µA
IL1 Light Current EV = 100lux 40 62.5 85 µA
IL2 Light Current EV = 10lux 6.2 µA
ILEAK Dark Current EV = 0lux 10 pA
VO(MAX) Maximum Output Compliance Voltage at 95% of nominal output current, EV = 100lux 2.7 V
tRRise Time (Note 2) RL = 5kΩ, EV = 300lux 105 µs
RL = 1kΩ, EV = 1000lux 64 µs
tFFall Time (Note 2) RL = 5kΩ, EV = 300lux 170 µs
RL = 1kΩ, EV = 1000lux 77 µs
tDDelay Time for Rising Edge (Note 2) RL = 5kΩ, EV = 300lux 165 µs
RL = 1kΩ, EV = 1000lux 112 µs
tSDelay Time for Falling Edge (Note 2) RL = 5kΩ, EV = 300lux 65 µs
RL = 1kΩ, EV = 1000lux 33 µs
VLO Maximum Voltage at EN Pin to Enable 0.6 V
VHI Minimum Voltage at EN Pin to Disable 1.8 V
ILO Input Current at EN Pin VEN = 0V 0.01 µA
IHI Input Current at EN Pin VEN = 3V 2 µA
tEN Enable Time EV = 200lux 140 µs
tDIS Disable Time EV = 200lux 2 µs
NOTES:
2. Switching time measurement is based on Figures 1 and 2.
3. Fluorescent light is substituted by Green LED during production
EL7900
3FN7377.8
September 18, 2009
EL7900
PULSE
DRIVE
VCC
RL
VOUT
FIGURE 1. RISE/FALL TIME MEASUREMENT
CH1
CH2
PULSE DRIVE
VOUT
tD
tR
80%
20%
tS
tF
1ms
1V
0.5V
VS = 3V
TA = +27°C
FIGURE 2. RISE/FALL TIME MEASUREMENT WAVEFORMS
Typical Performance Curves
FIGURE 3. SPECTRAL RESPONSE FIGURE 4. SENSITIVITY
FIGURE 5. DARK CURRENT vs TEMPERATURE FIGURE 6. GAIN vs TEMPERATURE
0
20
40
60
80
100
400 500 600 700 800 900 1k
WAVE LENGTH (nm)
RELATIVE RESPONSE (%)
EL7900 RELATIVE RESPONSE
EL7900 RELATIVE
RESPONSE WITH IR
GLASS FILTER
ILLUMINATION (L X)
OUTPUT CURRENT (µA)
700
600
400
200
0
500
300
100
0 200 400 600 800 1000
VCC = 3V
FLUORESCENT LIGHT
-4000
-3000
-2000
-1000
0
1000
-45-35-25-15-5 5 1525354555657585
IOUT (pA)
TEMPERATURE (°C)
VDD = 5V
VDD = 3.3V
TEMPERATURE (°C)
GAIN/GAIN (+25°C)
1.20
1.15
0.95
0.80
1.05
0.85
-60 -40 0 40 80 100-20 20 60
1.10
0.90
1.00
VDD = 3V
FLUORESCENT LIGHT OF 50lux
EL7900
4FN7377.8
September 18, 2009
Block Diagram
FIGURE 7. OUTPUT COMPLIANCE VOLTAGE vs CURRENT FIGURE 8. RADIATION PATTERN
FIGURE 9. IOUT vs LUMINANCE
Typical Performance Curves
OUTPUT CURRENT (µA)
OUTPUT COMPLIANCE VOLTAGE
(VDD - VOUT) (V)
0.6
0.5
0.2
0
0.3
0.1
-200 0 400 800 1000 1200200 600
VDD = 3V
TA = +27°C
0.4
RADIATION PATTERN
LUMINOSITY
ANGLE
RELATIVE SENSITIVITY
90°
80°
70°
60°
50°
40° 30° 20° 10° 0°
90°
80°
70°
60°
50°
40°
30°
20°
10°
0.20.4 0.60.81.0
0
1
2
3
4
5
0 1k2k3k4k5k6k7k8k9k10k
LUMINANCE (lux)
IOUT (mA)
FLUORESCENT
LIGHT SOURCE
Pin Descriptions
PIN NAME DESCRIPTION
1 VCC Supply, 2.7V to 5.5V
2 GND Ground
3EN
Enable
4 NC No connect
5 Output Current output pin
ENABLE
OUTPUT
GND
VCC
1
2
5
3
EL7900
5FN7377.8
September 18, 2009
Application Information
Product Descr iption
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 100lux 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 intercep ted 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, IOUT is the output current in µA, and LINPUT is the
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 Equation 2:
Here, VOUT is the output voltage and RLOAD is the value of
the load resistor ad ded. The compliance of the EL7900's
output circuit may result in prematur e saturation of the
output current and voltage when an excessively large
RLOAD is used. The output compliance voltage is 300mV
below the supply voltage as listed in VO(MAX) of the
Electrical Specificatio ns table on page 2.
In order to have the line ar 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
Equation 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. Fo r maximum dynamic range or
swing, choose a higher value RLOAD. Although finite, the
output impedance of the devi ce is con siderably 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. Wh en 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 300 mV below the
supply. The output current stops ramping when the output
voltage reaches voltage compliance.
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 contro l 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 show s a fully automatic di mming
solution with no user interactio n. 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. T he 0.25V represents the minimum LED
IOUT 60μA
100lux
-------------------
⎝⎠
⎛⎞
LINPUT
×=(EQ. 1)
VOUT IOUT RLOAD
×60μA
100lux
-------------------
⎝⎠
⎛⎞
LINPUT RLOAD
××== (EQ. 2)
RLOAD VSUP 0.3V–()
60μA
---------------------------------------100lux
LRANGE
-----------------------
×=
(EQ. 3)
TABLE 1. VDD = 5V, MAXIMUM OUTPUT VOLTAGE = 4.7V
ILLUMINA TION 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
EL7900
6FN7377.8
September 18, 2009
brightness and 1.25V represents the maximum. The first
step would be to determi ne the ratio of R1 and R2:
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, R 2 can be
calculated as shown in Equations 5 and 6:
and
In Figure 11, 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 limit range via the 3V PWM
control.
Figure 12 shows how a fully manual override can be quickly
added by using the EN pin.
Short Circuit Current Limit
The EL7900 does not limit the output short circuit current. If
the output is directly shorted to the ground continuously, the
output current could easily incre ase for a strong input light
such that the device may be damaged. Maximum reliability is
maintained if the output continuous current never exceeds
6mA by adding a load resistor at the output. This limit is set
by the design of the internal metal interconnects.
Suggested PCB Footprint
Footprint pads should be a nominal 1-to-1 correspondence
with package pads. The large, exposed central die-mounting
paddle in the center of the package requires neither thermal
nor electrical connections to PCB, and such connections
should be avoided.
Power Supply Bypassing and Printed Circuit
Board Layout
The EL7900 is relatively insensitive to the printed circuit
board layout due to its low speed operation. Nevertheless,
good printed circuit board layout is necessary for optimum
performance. Ground plane construction is highly
recommended, lead length should be as short as possible
and the power supply pins must be well bypassed to reduce
the risk of oscillation. For normal single supply operation,
where the GND pin is connected to ground, a 0.1µF ceramic
capacitor should be placed from VCC pin to GND pin. A
4.7µF tantalum capacitor should then be connected in
parallel, placed close to the device.
R1R23.0V
0.25V
----------------1–
⎝⎠
⎛⎞
×11 R2
×== (EQ. 4)
3V TO 5V
SUPPLY VOLTAGE 3V DC VOLTAGE
EL7900 OUTEN
GND
VDO
TO INVERTER BRIGHTNESS
CONTROLLER
C1
R2
R1
FIGURE 10. AUTOMATIC DIMMING SOLUTION
10k 25µF
110k
INPUT OR LED DRIVER
R21.25V
125μA
------------------
⎝⎠
⎛⎞
10kΩ== (EQ. 5)
R111 R2
×110kΩ== (EQ. 6)
3V TO 5V
SUPPLY VOLTAGE 3V PWM CONTROL
EL7900 OUTEN
GND
VDO
FIGURE 1 1. AUTOMA TIC DIMMING SOLUTION WITH
ADJUSTABLE BIAS CONTROL
C1
R2
R1
10k 25µF
110k
TO INVERTER BRIGHTNESS
CONTROLLER
INPUT OR LED DRIVER
3V TO 5V
SUPPLY VO LTAGE 3V PWM CONTRO L
EL7900 OUTEN
GND
VDO
FIGURE 12. AUTOMA TIC DIMMING SOLUTION WITH
ADJUSTABLE BIAS CONTROL AND MANUAL
OVERRIDE
ENABLE/
CONTROL
DISABLE
C1
R2
R1
10k 25µF
110k TO IN VERTER
CONTROLLER
BRIGHTNESS
LED DRIVER
INPUT OR
EL7900
7
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No lice nse is gran t ed by i mpli catio n or other wise u nder an y p a tent or patent right s of Int ersi l or it s sub sidi aries.
For information regarding Intersil Corporation and its products, see www.intersil.com
FN7377.8
September 18, 2009
FIGURE 13. EL7900 SENSOR DIAGRAM
EL7900
8FN7377.8
September 18, 2009
EL7900
Package Outline Drawing
L5.2x2.1
5 LEAD OPTICAL DUAL FLAT NO-LEAD PLASTIC PACKAGE
Rev 1, 05/08
located within the zone indicated. The pin #1 identifier may be
Unless otherwise specified, tolerance : Decimal ± 0.05
Tiebar shown (if present) is a non-functional feature.
The configuration of the pin #1 identifier is optional, but must be
between 0.15mm and 0.30mm from the terminal tip.
Dimension b applies to the metallized terminal and is measured
Dimensions in ( ) for Reference Only.
Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
6.
either a mold or mark feature.
3.
5.
4.
2.
Dimensions are in millimeters.1.
NOTES:
BOTTOM VIEW
DETAIL "X"
SIDE VIEW
TYPICAL RECOMMENDED LAND PATTERN
TOP VIEW
1
2
3
5
4
(4X) 0.10
INDEX AREA
PIN 1
A
2.10
B
2.00
PIN #1 INDEX AREA
5X 0 . 35 ± 0 . 05 B0.10 MAC
C
SEATING PLANE
BASE PLANE
0.08
0.10
SEE DETAIL "X"
C
C
0 . 00 MIN.
0 . 05 MAX.
0 . 2 REF
C5
1
( 5X 0 . 30 )
( 5X 0 . 55 )
6
6
(0.65)
(1.95)
(0.65)
(1.35)
0.65
1.35 1.30 REF
0.65
0.30±0.05
0 . 7 ± 0 . 05
