SDP8476-201
Low Light Rejection Phototransistor
FEATURES
•
Side-looking plastic package
•
Low light level immunity
•
50¡ (nominal) acceptance angle
•
Mechanically and spectrally matched to
SEP8506 and SEP8706 infrared emitting diodes
INFRA-21.TIF
DESCRIPTION
The SDP8476 is an NPN silicon phototransistor which
internal base- emitter shunt resistance. Transfer molding
of this device in a clear T- 1 plastic package assures
superior optical centerline performance compared to
other molding processes. Lead lengths are staggered to
provide a simple method of polarity identification.
Distinguising Feature:
This device incorporates all of the desired features of a
standard phototransistor with the advantage of low light
immunity. The phototransistor switching occurs when
the incident light increases above the threshold (knee
point). When the light level exceeds the knee point of
the device, it will function as a standard phototransistor.
Chart A illustrates the light current output of the low light
rejection phototransistor as compared to a standard
phototransistor with similar sensitivity.
Typical Application Uses:
Ideally suited for use in applications which require
ambient light rejection, or in transmissive applications
where the interrupter media is semi- transparent to
infrared energy. This device also provides high contrast
ratio in reflective applications where unwanted
background reflection is a possibility.
OUTLINE DIMENSIONS
in inches (mm)
Tolerance
3 plc decimals
±0.005(0.12)
2 plc decimals
±0.020(0.51)
DIM_017.ds4
142
h
Honeywell reserves the right to make
changes in order to improve design and
supply the best products possible.
SDP8476-201
Low Light Rejection Phototransistor
ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
TEST CONDITIONS
ABSOLUTE MAXIMUM RATINGS
(25¡C Free-Air Temperature unless otherwise noted)
Collector-Emitter Voltage
Power Dissipation
Operating Temperature Range
Storage Temperature Range
Soldering Temperature (5 sec)
30 V
100 mW [À]
-40¡C to 85¡C
-40¡C to 85¡C
240¡C
SCHEMATIC
Notes
1. Derate linearly from 25¡C free-air temperature at the rate of
0.78 mW/¡C.
Honeywell reserves the right to make
changes in order to improve design and
supply the best products possible.
h
143
SDP8476-201
Low Light Rejection Phototransistor
SWITCHING TIME TEST CIRCUIT
cir_015.cdr
SWITCHING WAVEFORM
cir_004.cdr
Fig. 1
Responsivity vs
Angular Displacement
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-60
-45
-30
-15
0
Fig. 2
gra_054.ds4
Spectral Responsivity
gra_036.ds4
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
400
600
800 1000 1200
+15 +30 +45 +60
Angular displacement - degrees
Fig. 3
Dark Current vs
Temperature
Fig. 4
gra_310.ds4
Relative response
Relative response
Wavelength - nm
Collector Current vs
Ambient Temperature
2.0
gra_039.ds4
1000
100
10
1
0.1
0.01
-55 -35 -15
5
25
45
65
85 105 125
Vce = 15
H=0
Normalized collector
current
Dark Current - nA
1.6
1.2
0.8
0.4
0.0
0
10
20
30
40
50
60
70
80
Free-air temprerature - °C
All Performance Curves Show Typical Values
Ambient temperature - °C
144
h
Honeywell reserves the right to make
changes in order to improve design and
supply the best products possible.
SDP8476-201
Low Light Rejection Phototransistor
Chart A. Low Light Rejection Phototransistor vs. Standard Phototransistor
6.00
5.00
Light current - mA
4.00
3.00
2.00
1.00
0.00
0.00
Min. Light
Current Slope
Max. Light
Current Slope
Min. Light
Current Slope
Standard
Max. Light
Current Slope
Standard
0.25
0.50
Source intensity - mW/cm
2
0.75
1.00
Designing with the Low Light Rejection
Phototransistor:
The Low Light Rejection detector is tested at different
incident light levels to determine adherence to the
specified knee point and light current slope. This method
assures proper functionality vs. standard
phototransistors, and guarantees required light current
output.
The light current slope is the change in light current
output at two given source irradiances divided by the
change in the two source irradiances.
(Formula
# 1)
I
L
Slope = [I
L 1
(@ H
1
) - I
L2
(@ H
2
)] / [H
1
- H
2
]
Where:
2
•
I
L
slope is the light current slope in mA/mW/cm
•
I
L
is the light current output in mA
2
•
H is the source intensity in mW/cm
Chart A shows the specified limits of light current slope
for the low light rejection phototransistor which begins its
2
slope at the typical knee point, 0.25mW/cm . To make a
clear distinction between this device and a standard
phototransistor, light current slopes for high and low
sensitivity standard phototransistors are also shown.
Note that for phototransistors of the same gain, the
slopes of the two products are parallel.
The knee point, the source irradiance needed to increase
I
L
to 50uA, is a necessary parameter for circuit design.
All variation in the knee point will be offset by the
internally guardbanded light current slope limits. The
appropriate formula for circuit design is the following:
(Formula
# 2)
I
L
= I
L
slope
MIN.
* (H
A
- H
KP
)
Where:
•
I
L
is the light current output in mA
•
I
L
slope
MIN.
is the minimum limit on the light current
2
slope (i.e. 1.0mA/mW/cm )
•
H
A
is the source light incident on the detector for the
application
•
H
KP
is the specified level of source light incident on
the detector at the typical knee point (i.e. 0.125
2
mW/cm )
To design a transmissive sensor with two of Honeywell’s
standard components, the SEP8506-003 and the
SDP8476-201, it is first necessary to determine the
2
irradiance level in mW/cm that will be incident on the
detector. The application conditions are the following:
Honeywell reserves the right to make
changes in order to improve design and
supply the best products possible.
145
SDP8476-201
Low Light Rejection Phototransistor
Supply voltage = 5V
Distance between emitter and detector = 0.535 in.
(13.6mm)
IRED drive current = 20mA
The SEP8506-003 gives 0.45mW/cm min. to
2
0.90mW/cm max. under the above conditions. To obtain
minimum light current output, use the minimum irradiance
limit.
Light current output = I
L
slope
MIN.
* (H
A
- H
KP
)
2
Light current output = 1.0 mA/mW/cm min. *
2
2
(0.45mW/cm min. - 0.25 mW/cm ) = 0.2mA min.
2
146
Honeywell reserves the right to make
changes in order to improve design and
supply the best products possible.
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