Description
The AEDR-8400 encoder is the smallest optical encoder
employing reective technology for motion control
purposes. The encoder houses an LED light source and a
photo-detecting circuitry in a single package.
The AEDR-8400 encoder oers 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 exibility and easy integration
into existing systems.
Features
• Reective 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)
Applications
Ideal for high volume applications:
• Printers
• Copiers
• Card readers
• Scanners
• Digital Still Cameras
• Camcorders
• Camera Phones
• Projectors
• Consumer Product Applications
AEDR-8400 Series
Reective Surface Mount Optical Encoder
Data Sheet
Disclaimer: This product is not certied 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.
2
State Width Error (∆S): The deviation of state width, in elec-
trical 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 de-
gree, 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 elec-
trical degree, from its ideal value of 180°e.
Count (N): The number of window and bar pair per revolu-
tion (CPR) of codewheel. For linear codestrip, dened as
the number of window and bar pair per unit length (lines
per inch [LPI] or lines per mm [LPmm]).
One Cycle (C): 360 electrical degrees (°e). Equivalent to one
window and bar pair.
One Shaft Rotation: 360 mechanical degrees. Also equiva-
lent 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 mo-
tion, mechanical displacement in the radial and tangen-
tial 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
reected by a surface. Quantied in terms of the per-
centage of incident light. A spectrometer can be used
to measure specular reectance of a surface (contact
factory for more information).
V
LED
Gnd
V
CC
Ch A
Ch B
Gnd Codestrip or
Note: Drawing not to scale.
Signal
Processing
Circuitry
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 reective
area (window) of the codewheel (or codestrip) reects
light back to the photodetector IC, whereas no light is
reected by the non-reective 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 mo-
tor, 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.
Denitions
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.
Theory of Operation
The AEDR-8400 encoder combines an emitter and a de-
tector 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
Codestrip or Codewheel
Tangential (ET)
Shaft
Radial (ER
)
)
Codewheel
AEDR-8400
Shaft
Angular (EA)
Codewheel
AEDR-8400
Note: Drawing not to scale
Gap
3
Notes:
1. Exposure to extreme light intensity (such as from ashbulbs 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.
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.
Recommended Operating Conditions
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
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 CL100 pF 2.7 kΩ Pull-Up
Count Frequency3F 15 kHz
Radial Misalignment ER±0.2 mm
Tangential Misalignment ET±0.2 mm
Angular Misalignment EA0 ±1.5 deg.
Codewheel/strip Tilt CT0 1 deg.
Codewheel/strip Gap G 0.23 0.43 0.63 mm
Output waveform
4
Electrical Characteristics
Characteristics over recommended operating conditions at 25°C.
Recommended Codewheel and Codestrip Characteristics
Notes:
1. Measurements from SMS µScan System. Contact factory for more information.
2. Contact factory for more information on compatibility of codewheel/strip.
Parameter Symbol Min. Typ. Max. Unit Notes
Detector Supply Current Icc 6.0 7.0 mA
High Level Output Voltage VOH 2.4 V IOH = -0.2mA
Low Level Output Voltage VOL 0.4 V IOL = 8.0mA
Rise Time tr400 ns CL = 25pF
Fall Time tf120 ns RL = 2.7kΩ
Parameter Symbol Min. Max. Unit Notes
Window/bar Ratio Ww/Wb 0.9 1.1
Window/bar Length LW1.80 (0.071) 2.31 (0.091) mm (inches)
Specular Reectance Rf60 - Reective area.
See note 1.
- 10 Non reective area
Line Density LPmm (LPI) 10 (254)
12.5 (318)
lines/mm (inch)
Optical radius Rop 11 - mm Recommended
Rop=11.0mm
Encoding Characteristics
Encoding characteristics over the recommended operating condition and mounting conditions.
Note:
1. Typical values represent the encoder performance at typical mounting alignment, whereas the maximum values represent the encoder perfor-
mance across the range of recommended mounting tolerance.
Parameter Symbol Typical Maximum Unit
Pulse Width Error (Channel A) ∆P 10 75 °e
Pulse Width Error (Channel B) ∆P 11 80 °e
Phase Error ∆φ 7 60 °e
LW
WW, Reflective area Wb, Non-reflective area
WW = WB = 50µm (254LPI)
Codestrip = 40µm (318LPI)
5
Outline Drawing
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 specied to moisture sensitive level (MSL) 3.
Encoder option Pin 1 Pin2 Pin3 Pin4 Pin5 Pin6
AEDR-8400 VLED Gnd Ch B Ch A VCC GndLED
Encoder Pin Conguration
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
6
Encoder Orientation
The AEDR-8400 is designed such that both the emitter
and detector IC should be placed parallel to the win-
dow/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
Linear Scale
Rotation
Linear Scale
Top View
Note: Drawing not to scale.
Anti-clockwise
Ch. A leads
Ch. B
emitter
Codewheel
Clockwise
Ch. B leads
Ch. A
emitter
Codewheel
Note: Drawing not to scale.
Top View
Ch. B leads
Ch. A
emitter
To left
Codestrip
To right
emitter
Ch. A leads
Ch. B
Codestrip
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 cen-
ter 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.
Recommended Land Pattern for AEDR-8400
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 resis-
tor is necessary to prevent excess current from owing
through the emitter. Refer page 6.
Common ground
routin
g
PCB/FPC
Legend:
Possible common ground routing:
Pin 1 (VLED)
Pin 2 (Gnd)
Pin 3 (Ch B) (Ch A) Pin 4
(VCC) Pin 5
(GndLED) Pin 6
8
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
Recommended Lead-free Reow Soldering Temperature Prole
Note: Encoders are packed in tape of quantity 1000pcs or 100pcs
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 reow.
Ordering Information
AEDR-84 Option
Lines per inchPackaging Shipping UnitsNumber of Channels
0
0 – Two channels 1 – Tape and reel 3 – 254 LPI 0 – 1000 pcs
2 – 100 pcs
4 – 318 LPI
AEDR-8400 LED Specications
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.