AVAGO AEDR-8400-132 Reflective surface mount optical encoder Datasheet

AEDR-8400 Series
Reflective Surface Mount Optical Encoder
Data Sheet
Description
Features
The AEDR-8400 encoder is the smallest optical encoder
employing reflective technology for motion control
purposes. The encoder houses an LED light source and a
photo-detecting circuitry in a single package.
• Reflective technology
• Surface mount leadless package
• Two channel quadrature digital outputs for direction
sensing
• TTL compatible
• Single 2.8V supply
• -20°C to 85°C absolute operating temperature
• Encoding resolution:
254 (lines/inch) or 10 (lines/mm)
318 (lines/inch) or 12.5 (lines/mm)
The AEDR-8400 encoder offers two-channel quadrature
digital outputs. Being TTL compatible, the outputs of the
AEDR-8400 encoder can be interfaced directly with most
of the signal processing circuitries. Hence the encoder
provides great design-in flexibility and easy integration
into existing systems.
Applications
Ideal for high volume applications:
• Printers
• Copiers
• Card readers
• Scanners
• Digital Still Cameras
• Camcorders
• Camera Phones
• Projectors
• Consumer Product Applications
Disclaimer: This product is not certified or warrantied for automotive applications. If the customer
intends to use it for automotive applications, they do so at their own risk. Avago will not be
responsible for any claim of product failure during operation or reliability assessment.
Theory of Operation
The AEDR-8400 encoder combines an emitter and a detector in a single surface mount leadless package. When
used with a codewheel or linear codestrip, the encoder
translates rotary or linear motion into digital outputs.
As seen in the block diagram, the AEDR-8400 consists
of three major components: a light emitting diode (LED)
light source, a detector IC consisting photodiodes and
lens to focus light beam from the emitter as well as light
falling on the detector.
Block Diagram of AEDR-8400 Encoder
V LED
State Width Error (∆S): The deviation of state width, in electrical degree, from its ideal value of 90°e.
Phase (φ): The number of electrical degrees between the
center of high state of Channel A and the center of high
state of Channel B. Nominally 90°e.
Phase Error (∆φ): The deviation of phase, in electrical degree, from its ideal value of 90°e.
Pulse Width (P): The duration of high state of the output,
in electrical degree, within one cycle. Nominally 180°e
or half a cycle.
Pulse Width Error (∆P): The deviation of pulse width, in electrical degree, from its ideal value of 180°e.
Gnd
Count (N): The number of window and bar pair per revolution (CPR) of codewheel. For linear codestrip, defined as
the number of window and bar pair per unit length (lines
per inch [LPI] or lines per mm [LPmm]).
VCC
Signal
Processing
Circuitry
Ch A
Ch B
Gnd
Note: Drawing not to scale.
Codestrip or
Codewheel
The operation of the encoder is based on the principle
of optics where the detector photodiodes sense the
absence and presence of light. In this case, the rotary/
linear motion of an object being monitored is converted
to equivalent light pattern via the use of codewheel/
codestrip. As shown in the above diagram, the reflective
area (window) of the codewheel (or codestrip) reflects
light back to the photodetector IC, whereas no light is
reflected by the non-reflective area (bar). An alternating
light and dark patterns corresponding to the window and
bar fall on the photodiodes as the codewheel rotates. The
moving light pattern is exploited by the detector circuitry
to produce digital outputs representing the rotation of
the codewheel. When the codewheel is coupled to a motor, the encoder outputs are then a direct representation
of the motor rotation. The same concept applies to the
use of a codestrip to detect linear motion.
Definitions
State Width (S): The number of electrical degrees between
a transition in Channel A and the neighboring transition
in Channel B. There are 4 states per cycle, each nominally
90°e.
Radial (ER))
One Shaft Rotation: 360 mechanical degrees. Also equivalent to N counts (codewheel only).
Line Density: The number of window and bar pair per unit
length, expressed in either lines per inch (LPI) or lines
per mm (LPmm).
Optical radius (Rop): The distance between the codewheel
center and the center of the encoder dome.
Gap (G): The distance from surface of the encoder to the
surface of codewheel or codestrip.
Radial and Tangential Misalignment Error (ER, ET): For rotary motion, mechanical displacement in the radial and tangential directions relative to the nominal alignment.
Angular Misalignment Error (EA): Angular displacement of the
encoder relative to the tangential line.
Specular Reflectance (Rf ): The amount of incident light
reflected by a surface. Quantified in terms of the percentage of incident light. A spectrometer can be used
to measure specular reflectance of a surface (contact
factory for more information).
Angular (EA)
Tangential (ET)
AEDR-8400
One Cycle (C): 360 electrical degrees (°e). Equivalent to one
window and bar pair.
Codestrip or Codewheel
AEDR-8400
Shaft
Shaft
Codewheel
Codewheel
Gap
Note: Drawing not to scale
Output waveform
Absolute Maximum Ratings
Storage Temperature, TS
-40°C to 85°C
Operating Temperature, TA
-20°C to 85°C
Supply Voltage, VCC
-0.5 V to 7 V
Output Voltage, VO
-0.5 V to VCC
Output Current per Channel, IOUT
-1.0 mA to 8 mA
ESD
Human Body Model JESD22-A114-A Class 3A
Machine Model JESD22-A115-A Class B
Notes:
1. Exposure to extreme light intensity (such as from flashbulbs or spotlights) may cause permanent damage to the device.
2. CAUTION: It is advised that normal static precautions should be taken when handling the encoder in order to avoid damage and/or degradation
induced by ESD.
3. Proper operation of the encoder cannot be guaranteed if the maximum ratings are exceeded.
Recommended Operating Conditions
Parameter
Symbol
Min.
Typ.
Max.
Units
Notes
Temperature
TA
-20
25
85
°C
See note 1
Supply Voltage
VCC
2.6
2.8
3.0
V
Ripple < 100mVp-p
LED Current
ILED
5
6
8
mA
See note 2
Load Capacitance
CL
100
pF
2.7 kW Pull-Up
Count Frequency3
F
15
kHz
Radial Misalignment
ER
±0.2
mm
Tangential Misalignment
ET
±0.2
mm
Angular Misalignment
EA
0
±1.5
deg.
Codewheel/strip Tilt
CT
0
1
deg.
Codewheel/strip Gap
G
0.43
0.63
mm
0.23
Notes:
1. Refer to AEDR-8400 Reliability Datasheet
2. LED Current Limiting Resistor: Recommended series resistor = 121Ω (±1%) for 254 LPI and 255Ω (±1%) for 318 LPI.
3. Count frequency = velocity (rpm) x N / 60.
Encoding Characteristics
Encoding characteristics over the recommended operating condition and mounting conditions.
Parameter
Symbol
Typical
Maximum
Unit
Pulse Width Error (Channel A)
DP
10
75
°e
Pulse Width Error (Channel B)
DP
11
80
°e
Phase Error
Df
7
60
°e
Note:
1. Typical values represent the encoder performance at typical mounting alignment, whereas the maximum values represent the encoder performance across the range of recommended mounting tolerance.
Electrical Characteristics
Characteristics over recommended operating conditions at 25°C.
Parameter
Symbol
Detector Supply Current
Icc
High Level Output Voltage
VOH
Low Level Output Voltage
VOL
Rise Time
tr
Fall Time
tf
Min.
Typ.
Max.
Unit
6.0
7.0
mA
2.4
Notes
V
IOH = -0.2mA
V
IOL = 8.0mA
400
ns
CL = 25pF
120
ns
RL = 2.7kW
0.4
Recommended Codewheel and Codestrip Characteristics
WW = WB = 50µm (254LPI)
= 40µm (318LPI)
Codestrip
LW
WW, Reflective area
Wb, Non-reflective area
Parameter
Symbol
Min.
Max.
Window/bar Ratio
Ww/Wb
0.9
1.1
Window/bar Length
LW
1.80 (0.071)
2.31 (0.091)
Specular Reflectance
Rf
60
-
Reflective area.
See note 1.
-
10
Non reflective area
Line Density
LPmm (LPI)
10 (254)
12.5 (318)
Optical radius
Rop
11
Notes
mm (inches)
lines/mm (inch)
-
Notes:
1. Measurements from SMS µScan System. Contact factory for more information.
2. Contact factory for more information on compatibility of codewheel/strip.
Unit
mm
Recommended
Rop=11.0mm
LED Current Limiting Resistor
A resistor to limit current to the LED is required. The recommended value is 121Ω (±1%) for 254 LPI and 255Ω (±1%)
for 318 LPI. The resistor should be placed in series between the 2.8 V supply and pin 1 of the device (VLED). This will
result in an LED current of approximately 6mA.
Moisture Sensitive Level
The AEDR-8400 is specified to moisture sensitive level (MSL) 3.
Outline Drawing
Pin 1 Indication (Top View):
i) Refer to the incorporated chamfer, or
ii) Refer to the upper left pin closer to the emitter;
as shown in the diagram.
* All dimensions in millimeter.
Tolerance x.xx ± 0.10 mm.
Bottom View
Encoder Pin Configuration
Encoder option
Pin 1
Pin2
Pin3
Pin4
Pin5
Pin6
AEDR-8400
VLED
Gnd
Ch B
Ch A
VCC
GndLED
Encoder Orientation
The AEDR-8400 is designed such that both the emitter
and detector IC should be placed parallel to the window/bar orientation, as shown. As such, the encoder is
tolerant against radial play of ± 0.20mm.
Direction of Movement
With the emitter side of the encoder placed closer to the
codewheel centre, Channel A leads Channel B when the
codewheel rotates anti-clockwise and vice versa.
Rotation
Codewheel
Codewheel
Top View
Ch. A leads
Ch. B
emitter
Anti-clockwise
Ch. B leads
Ch. A
emitter
Clockwise
Note: Drawing not to scale.
Rotation
Linear Scale
Codestrip
Codestrip
Top View
emitter
Ch. A leads
Ch. B
To right
emitter
Ch. B leads
Ch. A
Note: Drawing not to scale.
To left
Linear Scale
Recommended Land Pattern for AEDR-8400
AEDR-8400 Pad Soldering
In order to provide adequate mechanical strength for the
AEDR-8400 encoder, it is strongly recommended the all
pin-outs need to be soldered including the encoder center pad. However, external circuit routing on PCB / FPC
could actually route pin 2, pin 6 and center pad together
hence to have a common ground for the encoder. This
could help to simplify the circuitry routing.
Likewise, the emitter input voltage supply (Vled) could
share a common voltage supply with detector IC voltage
supply (Vcc) i.e. 2.8V typically. Note that a series resistor is necessary to prevent excess current from flowing
through the emitter. Refer page 6.
Possible common ground routing:
(GndLED) Pin 6
Pin 1 (VLED)
(VCC) Pin 5
Pin 2 (Gnd)
(Ch A) Pin 4
Pin 3 (Ch B)
Legend:
PCB/FPC
Common ground
routing
AEDR-8400 LED Specifications
The AEDR-8400 254 LPI is using the AIGalnP LED with
typical wavelength at 624nm. The AEDR-8400 318 LPI
is using the IR base LED with typical wavelength at
870nm.
Recommended Lead-free Reflow Soldering Temperature Profile
Preheat Temperature 40 °C to 125 °C
= 120 sec max
Temperature maintain above 217 °C
= 60 – 150 sec
Peak Temperature
= 255 ± 5°C
Time above 250 °C
= 10 – 20 sec
Note: Due to treatment of high temperature, AEDR-8400 compound may turn yellow after IR reflow.
Ordering Information
AEDR-84
0
Option
Number of Channels
0 – Two channels
Packaging
1 – Tape and reel
Lines per inch
3 – 254 LPI
4 – 318 LPI
Shipping Units
0 – 1000 pcs
2 – 100 pcs
Note: Encoders are packed in tape of quantity 1000pcs or 100pcs
For product information and a complete list of distributors, please go to our web site:
www.avagotech.com
Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies, Limited in the United States and other countries.
Data subject to change. Copyright © 2006 Avago Technologies Limited. All rights reserved. Obsoletes AV01-0142EN
AV02-0262EN - April 18, 2007
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