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| AEDR-8320 Encoder Reflective Surface Mount Optical Encoder Data Sheet Description The AEDR-8320 encoder is an analog output encoder that employs optical reflective technology for rotary and linear movement control. With the introduction of reflective technology, encoder packages can now be made smaller and weigh significantly lighter. This statement is better reflected in the ability of the AEDR-8320 encoder which can easily fit into many space and weight constraint applications, e.g., CD or DVD writer laser head's linear movement. The AEDR-8320 comes in a 180 LPI (Lines Per Inch) or 7.09 mm lines per mm. In addition its 2-channel analog outputs can obtain higher resolution through interpolation of 2x, 4x, 8x or more. For example, with 8x interpolation, the final resolution of the encoder will yield 1,440 lines per inch, which is approximately 20 m accuracy. AEDR-8320 encoder enhances design flexibility and provides an easy-to-assemble solution to a wide variety of applications, while continuously ensuring reliability in performance. Features * * * * * * Reflective technology Surface mount leadless package Two-channel analog voltage output Lead free package -10C to 70C operating temperature Encoding resolution: 180 (lines/inch) or 7.09 (lines/mm) Applications * * * * Printers Copiers CD/DVD writer Card readers Theory of Operation The AEDR-8320 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 analog outputs. As shown in the block diagram below, the AEDR-8320 encoder 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. 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 analog 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 90e. State Width Error (DS): The deviation of state width, in electrical degree, from its ideal value of 90e. Phase (f): The number of electrical degrees between the center of high state of Channel A and the center of high state of Channel B. Nominally 90e. Phase Error (Df): The deviation of phase, in electrical degree, from its ideal value of 90e. Pulse Width (P): The duration of high state of the output, in electrical degree, within one cycle. Nominally 180e or half a cycle. Pulse Width Error (DP): The deviation of pulse width, in electrical degree, from its ideal value of 180e. 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]). One Cycle (C): 360 electrical degrees (e). Equivalent to one window and bar pair. 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). CODEWHEEL or CODESTRIP Block Diagram of AEDR-8320 VLED GND VCC CH A CH B SIGNAL PROCESSING CIRCUITRY R Optical radius (Rop): The distance between the codewheel center and the centerline between the two domes of the encoder. 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). GND RADIAL (ER) ANGULAR (EA) TANGENTIAL (ET) AEDR-8320 AEDR-8320 SHAFT SHAFT CODEWHEEL NOTE: DRAWING NOT TO SCALE CODEWHEEL 2 Output Waveform PXB SX1 SX2 SX3 SX4 PXA CH B VX12 CH A 2.5 V VPP VX34 CH B VX56 VX78 PA PB S1 S2 S3 S4 VOFFSET 2.5 V VP VPP 0V VM 3 Test Parameter Definitions Name State Width Symbol Definition S1, S2, S3, S4 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 90e. The transitions are determined by where the analog signal crosses the 2.5 V voltage level. DS1, DS2, DS3, DS4 PA, PB DPA, DPB SX1, SX2, SX3, SX4 The deviation, in electrical degrees, of each state width from its ideal value of 90e. The number of electrical degrees that an analog output is greater than 2.5 V during one cycle. This value is nominally 180e or 1/2 cycle. The deviation, in electrical degrees, of each pulse width from its ideal value of 180e. The number of electrical degrees between a transition in channel A and neighboring transition in channel B. There are 4 states per cycle, each nominally 90e. The transitions are determined by where the channel A analog signal crosses with channel B (or its complimentary) signal. The deviation, in electrical degrees of each state X width from its ideal value of 90e. Pulse X width A is the number of electrical degrees that analog A output is greater than analog B output during one cycle. Pulse X width B is the number of electrical degrees that analog B output is greater than analog A during one cycle. These value are nominally 180e or 1/2 cycle. The deviation, in electrical degrees of each pulse X width from its ideal value of 180e. The peak-to-peak signal magnitude in V of the analog signal. The offset in mV from the mid-point of the analog peak-to-peak signal to the zero voltage point. The value in V of the peak and valley of the analog signal (i.e., one-sided reading). The absolute difference between VP and VM of channel A or B. The intersections in V of channel A analog waveform with that of either channel B or its component. The offset in mV from the mid-point of the analog peak to peak signal to 2.5 V. Ration (in percentage) of maximum voltage deviation from a straight line connecting adjacent upper and lower crosspoint voltages to the difference between crosspoint voltages. State Width Error Pulse Width Pulse Width Error State X Width State X Width Error Pulse X Width DSX1, DSX2, DSX3, DSX4 PXA, PXB Pulse X Width Error Analog Peak-toPeak Analog Offset Analog Peak Voltage DPXA, DPXB VPP VOFFSET VPA, VPB VMA, VMB Analog Peak to Peak VPPA, VPPB Voltage Analog Crosspoint Voltage Analog Offset Voltage Linearity Error Vx12, Vx34 Vx56, Vx78 VOFFSETA, VOFFSETB DLinearity 4 Absolute Maximum Ratings Parameter Storage Temperature Operating Temperature Supply Voltage (Detector) Output Voltage DC Forward Current (LED) Reverse Voltage Symbol TS TA VCC Va , Vb ILED VR Min. -40 -10 -0.5 -0.5 Max. 85 70 7 Vcc + 0.4 40 5 Units C C V V mA V VF < 3 V IR = 100 A Notes Note: 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 Operating Temperature Supply Voltage (Detector) Output Frequency DC Forward Current (LED) Symbol T VCC F ILED Min. -10 4.75 NA 16 Typ. 25 5.0 5 20 Max. 70 5.25 20 30 Units C V kHz mA Ripple < 100 mV Vpp (Velocity (rpm) x N)/60 See note 1 Notes Note: 1. LED Current Limiting Resistor A resistor to limit current to the LED is required. For 3.3 V LED Supply Voltage: The recommended value series resistor is 47 (10%). For 5.0 V LED Supply Voltage: The recommended resistor value will be 110 (10%). This will result in an LED current of approximately 20 mA. Electrical Characteristics Parameter Characteristics over recommended operating conditions at 25C. Symbol ICC VF Min. NA NA Typical 5 2.6 Max. 8 3.0 Units mA V IF = 20 mA typical Notes Supply Current (Detector) LED Forward Voltage 5 Encoding Characteristics Encoding characteristics over the recommended operating condition and mounting conditions. Parameter State Width Error Pulse Width Error State X Width Error Pulse X Width Error Parameter Peak to Peak Voltage (Average) Analog Offset Voltage Linearity Error Symbol DS DP DSX DPX Max. 40 40 40 40 Symbol VPPA, VPPB VOFFSETA, VOFFSETB Linearity Unit e e e e Min. 0.8 -350 NA Typ. 1.5 NA 5.0 Max. 3.0 350 12.5 Unit V mV % Note: 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. Part Mounting Tolerances Min. Radial Misalignment from Nominal Tangential Misalignment from Nominal Gap Distances Between Codewheel and Detector IC Angular Misalignment -0.2 -0.2 0.8 -1 Typ. 0 0 1.5 0 Max. 0.2 0.2 2.0 1 Units mm mm mm deg 6 Recommended Codewheel and Codestrip Characteristics CODEWHEEL Wb Lw Rop CODESTRIP Ww = Wb = 70.5 m (180 LPI) Ww Lw Wb, NON-REFLECTIVE AREA Ww, REFLECTIVE AREA Parameter Window/Bar Ratio Window/Bar Length Specular Reflectance Line Density Optical Radius Symbol Ww/Wb LW Rf LPmm (LPI) Rop Min. 0.9 1.80 (0.071) 60 - Max. 1.1 2.31 (0.091) 85 10 7.09 (180) 11 Unit mm (inches) Notes Reflective area. See note 1. Non reflective area lines/mm (lines/inch) mm Recommended value Notes: 1. Measurements from TMA Scan meter. Contact factory for more information. 2. Contact factory for more information on compatibility of codewheel/strip. Moisture Sensitive Level The AEDR-8320 is specified to moisture sensitive level (MSL) 3. 7 Outline Drawing 0.75 2.70 4.20 CHAMFER 0.65 B VCC GND 6.50 GND 1.58 VLED A A GND BOTTOM VIEW TOP VIEW 1.69 DETECTOR EMITTER SIDE VIEW NOTES: 1. ALL DIMENSIONS IN MILLIMETERS. 2. TOLERANCE X.XX 0.15 mm. 8 Encoder Orientation The AEDR-8320 is designed such that both the LED and detector IC should be placed parallel to the window/bar orientation, as shown. As such, the encoder is tolerant against radial play of 0.20 mm. The emitter side should be placed closer to the rotating shaft. CODEWHEEL CODESTRIP DIRECTION OF RADIAL PLAY DIRECTION OF RADIAL PLAY NOTE: DRAWING NOT TO SCALE Mounting Consideration CODEWHEEL/CODESTRIP GAP ROP 11.00 mm (0.433 IN) < ROP < NOTE: DRAWING NOT TO SCALE 9 Direction of Codewheel Rotation 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. ANTI-CLOCKWISE EMITTER CH. A LEADS CH. B VIEWED FROM TOP CH. B LEADS CH. A EMITTER CLOCKWISE NOTE: DRAWING NOT TO SCALE Recommended Land Pattern for AEDR-8320 0.7 mm 1.6 mm 3.3 mm 0.9 mm NOTE: THE SHADED AREAS ARE THE LEADS FOR SOLDERING 10 Recommended Lead-Free Reflow Soldering Temperature Profile 300 250 TEMPERATURE (C) 200 150 125C 100 50 0 40C 1 22 45 66 87 108 129 150 171 192 213 235 256 278 299 320 341 363 384 10 - 20 SEC. 255C 250C 217C 120 SEC. MAX. 60 - 150 SEC. TIME (SEC.) HEAT UP SOLDER PASTE DRY SOLDER REFLOW COOL DOWN PREHEAT TEMPERATURE 40C to 125C TEMPERATURE MAINTAIN ABOVE 217C PEAK TEMPERATURE TIME ABOVE 250C = = = = 120 SEC. MAX. 60 - 150 SEC. 250 5C 10 - 20 SEC. Note: Due to treatment of high temperature, AEDR-8320 compound may turn yellow after IR reflow. Ordering Information AEDR-8320 Option ___ ___ ___ Shipping Units 0 - 1000 pcs 2 - 100 pcs Resolution Q - 180 LPI Packaging 1 - Tape and Reel Revision History Rev. 0 1 Date August 2006 February 2007 Note Preliminary datasheet creation Release data sheet For product information and a complete list of distributors, please go to our website: 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 (c) 2007 Avago Technologies Limited. All rights reserved. AV02-0233EN - August 10, 2007 |
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