DATASHEET

EL7900
®
Data Sheet
September 18, 2009
FN7377.8
Ambient Light Photo Detect IC
Features
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.
• Monolithic IC containing photodiode and amplifier
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.
• Fast response time - <200µs
• 1lux to 8,000lux range
• Converts light intensity to current
• 2.7V to 5.5V supply range
• Low supply current: 1µA
• Excellent output linearity of luminance
• Ultra-compact and light surface mount package
• Pb-free (RoHS compliant)
Pinout
Applications
EL7900
(5 LD ODFN)
TOP VIEW
• Mobile phones
• Notebook PCs
VCC 1
GND 2
5 OUTPUT
THERMAL
PAD
• Video cameras
4 NC
EN 3
• PDAs
• Digital cameras
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
L5.2x2.1
Tape and Reel
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.
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. 2005-2008. All Rights Reserved.
All other trademarks mentioned are the property of their respective owners.
EL7900
Absolute Maximum Ratings (TA = +25°C)
Thermal Information
Supply Voltage between VSD and GND . . . . . . . . . . . . . . . . . . . .6V
Maximum Continuous Output Current . . . . . . . . . . . . . . . . . . . . 6mA
ESD Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV
Thermal resistance (Typical, Note 1)
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
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
PARAMETER
VCC = 3V, TA = +25°C, unless otherwise specified.
DESCRIPTION
CONDITION
VDD
Power Supply Range
ICC1
Supply Current
ICC2
Supply Current When Disabled
IL1
Light Current
EV = 100lux
IL2
Light Current
EV = 10lux
ILEAK
Dark Current
VO(MAX)
Maximum Output Compliance Voltage
tR
Rise Time (Note 2)
tF
tD
tS
Fall Time (Note 2)
Delay Time for Rising Edge (Note 2)
Delay Time for Falling Edge (Note 2)
VLO
Maximum Voltage at EN Pin to Enable
VHI
Minimum Voltage at EN Pin to Disable
MIN
TYP
2.7
RL = 1kΩ, EV = 100lux
MAX
5.5
UNIT
V
68
µA
EV = 0lux
1
µA
EN = VHI
0.5
µA
40
62.5
85
µA
6.2
µA
EV = 0lux
10
pA
at 95% of nominal output current, EV = 100lux
2.7
V
RL = 5kΩ, EV = 300lux
105
µs
RL = 1kΩ, EV = 1000lux
64
µs
RL = 5kΩ, EV = 300lux
170
µs
RL = 1kΩ, EV = 1000lux
77
µs
RL = 5kΩ, EV = 300lux
165
µs
RL = 1kΩ, EV = 1000lux
112
µs
RL = 5kΩ, EV = 300lux
65
µs
RL = 1kΩ, EV = 1000lux
33
µs
0.6
1.8
V
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
2
FN7377.8
September 18, 2009
EL7900
1ms
PULSE DRIVE
CH1
VCC
tD
tS
1V
PULSE
DRIVE
EL7900
VS = 3V
TA = +27°C
VOUT
RL
0.5V
80%
20%
VOUT
CH2
tR
tF
FIGURE 2. RISE/FALL TIME MEASUREMENT WAVEFORMS
FIGURE 1. RISE/FALL TIME MEASUREMENT
Typical Performance Curves
700
EL7900 RELATIVE RESPONSE
VCC = 3V
600 FLUORESCENT LIGHT
OUTPUT CURRENT (µA)
RELATIVE RESPONSE (%)
100
80
60
40
EL7900 RELATIVE
RESPONSE WITH IR
GLASS FILTER
20
500
400
300
200
100
0
0
400
500
600
700
800
900
0
1k
200
WAVE LENGTH (nm)
400
600
800
1000
ILLUMINATION (LX)
FIGURE 3. SPECTRAL RESPONSE
FIGURE 4. SENSITIVITY
1000
1.20
IOUT (pA)
0
VDD = 5V
-1000
-2000
VDD = 3.3V
-3000
GAIN/GAIN (+25°C)
VDD = 3V
1.15 FLUORESCENT LIGHT OF 50lux
1.10
1.05
1.00
0.95
0.90
0.85
-4000
-45 -35 -25 -15 -5 5
15 25 35 45 55 65 75 85
TEMPERATURE (°C)
FIGURE 5. DARK CURRENT vs TEMPERATURE
3
0.80
-60
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
FIGURE 6. GAIN vs TEMPERATURE
FN7377.8
September 18, 2009
EL7900
Typical Performance Curves
OUTPUT COMPLIANCE VOLTAGE
(VDD - VOUT) (V)
0.6
0.5
VDD = 3V
TA = +27°C
RADIATION PATTERN
LUMINOSITY 30°
ANGLE
40°
0.4
0.3
20°
10°
0°
10°
20°
30°
40°
50°
50°
60°
0.2
60°
70°
0.1
0
-200
0
200
400
600
800
1000
1200
70°
80°
80°
90°
90°
0.2 0.4
0.6 0.8 1.0
RELATIVE SENSITIVITY
OUTPUT CURRENT (µA)
FIGURE 7. OUTPUT COMPLIANCE VOLTAGE vs CURRENT
FIGURE 8. RADIATION PATTERN
5
IOUT (mA)
4
3
FLUORESCENT
LIGHT SOURCE
2
1
0
0
1k
2k
3k 4k 5k 6k 7k
LUMINANCE (lux)
8k
9k
10k
FIGURE 9. IOUT vs LUMINANCE
Block Diagram
Pin Descriptions
PIN
NAME
1
VCC
Supply, 2.7V to 5.5V
2
GND
Ground
3
EN
Enable
4
NC
No connect
5
Output
VCC
DESCRIPTION
1
3
ENABLE
Current output pin
5
OUTPUT
2
GND
4
FN7377.8
September 18, 2009
EL7900
Application Information
Resistor Output RLOAD Selection
Product Description
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 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 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-tocurrent conversion is:
60μA
I OUT = ⎛ -------------------⎞ × L INPUT
⎝ 100lux⎠
(EQ. 1)
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:
60μA
V OUT = I OUT × R LOAD = ⎛ -------------------⎞ × L INPUT × R LOAD
⎝ 100lux⎠
(EQ. 2)
Here, VOUT is the output voltage and RLOAD is the value of
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
RLOAD is used. The output compliance voltage is 300mV
below the supply voltage as listed in VO(MAX) of the
Electrical Specifications table on page 2.
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
Equation 3:
( V SUP – 0.3V ) 100lux
R LOAD = --------------------------------------- × ----------------------60μA
L RANGE
(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.
5
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
FN7377.8
September 18, 2009
EL7900
brightness and 1.25V represents the maximum. The first
step would be to determine the ratio of R1 and R2:
3.0V
R 1 = R 2 × ⎛ ---------------- – 1⎞ = 11 × R 2
⎝ 0.25V
⎠
3V TO 5V
SUPPLY VOLTAGE
Figure 12 shows how a fully manual override can be quickly
added by using the EN pin.
3V TO 5V
SUPPLY VOLTAGE
(EQ. 4)
VDO
3V DC VOLTAGE
R1
110k
ENABLE/
DISABLE
CONTROL
VDO
R1
110k
OUT
R2
10k
GND
TO INVERTER BRIGHTNESS
INPUT OR LED DRIVER
CONTROLLER
C1
25µF
TO INVERTER
BRIGHTNESS
INPUT OR
CONTROLLER
EL7900
EN
OUT
EL7900
EN
3V PWM CONTROL
GND
R2
10k
C1
25µF
LED DRIVER
FIGURE 12. AUTOMATIC DIMMING SOLUTION WITH
ADJUSTABLE BIAS CONTROL AND MANUAL
OVERRIDE
FIGURE 10. AUTOMATIC DIMMING SOLUTION
Short Circuit Current Limit
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 as shown in Equations 5 and 6:
1.25V
R 2 = ⎛ ------------------⎞ = 10kΩ
⎝ 125μA⎠
(EQ. 5)
and
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 increase 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
R 1 = 11 × R 2 = 110kΩ
(EQ. 6)
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.
3V TO 5V
SUPPLY VOLTAGE
3V PWM CONTROL
VDO
R1
110k
EL7900
EN
OUT
GND
R2
10k
TO INVERTER BRIGHTNESS
INPUT OR LED DRIVER
CONTROLLER
C1
25µF
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.
FIGURE 11. AUTOMATIC DIMMING SOLUTION WITH
ADJUSTABLE BIAS CONTROL
6
FN7377.8
September 18, 2009
EL7900
FIGURE 13. EL7900 SENSOR DIAGRAM
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 license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
7
FN7377.8
September 18, 2009
EL7900
Package Outline Drawing
L5.2x2.1
5 LEAD OPTICAL DUAL FLAT NO-LEAD PLASTIC PACKAGE
Rev 1, 05/08
2.10
6
PIN #1 INDEX AREA
A
B
6
PIN 1
INDEX AREA
1
5
1
2.00
1.35
1.30 REF
2
0.65
0.30±0.05 4
(4X)
3
0.10
0.65
0.10 M C A B
5X 0 . 35 ± 0 . 05
TOP VIEW
BOTTOM VIEW
(0.65)
SEE DETAIL "X"
0.10 C
0 . 7 ± 0 . 05
C
( 5X 0 . 30 )
(0.65)
BASE PLANE
(1.35)
SEATING PLANE
0.08 C
SIDE VIEW
( 5X 0 . 55 )
C
0 . 2 REF
5
(1.95)
0 . 00 MIN.
0 . 05 MAX.
DETAIL "X"
TYPICAL RECOMMENDED LAND PATTERN
NOTES:
1.
Dimensions are in millimeters.
Dimensions in ( ) for Reference Only.
2. Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
3.
Unless otherwise specified, tolerance : Decimal ± 0.05
4.
Dimension b applies to the metallized terminal and is measured
between 0.15mm and 0.30mm from the terminal tip.
5. Tiebar shown (if present) is a non-functional feature.
6.
8
The configuration of the pin #1 identifier is optional, but must be
located within the zone indicated. The pin #1 identifier may be
either a mold or mark feature.
FN7377.8
September 18, 2009
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