AEAS-7000

Agilent AEAS-7000 Plug and Play Ultra-Precision Absolute Encoder 16-bit Gray Code Data Sheet Description The encoder IC consists of 13 signal photo diode channels and 1 monitor photo diode channel and is used for the optical reading of rotary carriers (i.e., discs). The photodiodes are accompanied with precision amplifiers plus additional circuitry. The monitor channel is used to drive a constant current source for the highly collimated IR illumination system. Functional Description Background The 13 signal channels are set up as: 1. Two precision defining signals (A0, A09), which are two 90° electrical shifted sine, cosine signals. These signals are conditioned to be compensated for offset and gain errors. After conditioning they are on chip interpolated (4 bit) and computed to an absolute 6 bit Gray code. Additionally, these Sin/Cos signals can be tapped as two true-differential analog outputs to be used at the system designer’s choice. 2. 11 analog (A1-A11) channels which are directly digitized by precison comparators with hysterisis tracking. The digitized signals are called D1-D11. An internal correction and synchronization module allows the composition of a true 16 bit gray code by merging the data bits of 1) and 2) by still keeping the code monotony. There is a Gray code correction feature for this encoder to counter any codewheel imperfection or misalignment. This Gray code correction can be disabled/enabled by the pin KORR. The gain and offset conditioning value of the sine and cosine wave has been on-chip preset by factory. This will compensate for mechanical sensor misalignment error. Features • Minumum mechanical alignment during installation • 2 Sine/Cosine true differential outputs with 1024 periods for unit alignment • Integrated highly collimated illumination system • 11 digital tracks plus 2 sin/cos tracks generate precise 16 bit Gray code • Ultra fast, 1 µs cycle for serial data output word equals 16 MHz • On-chip interpolation and code correction to compensate for mounting tolerance • MSB can be inverted for changing the counting direction • Internally built in monitor track for tracking the light level • Watch dog with alarm output • –25°C to +85°C operating temp. Applications • Rotary application up to 16 bit/ 360° absolute position • Rotary application up to 11 bit user defined code patterns • Cost effective solution for direct integration into OEM systems Signal-Channels A1-A11 The photocurrent of the photo diodes is fed into a transimpedance amplifier. The analog output of the amplifier has a voltage swing of (dark/ light) about 1.3 V. Every output is transformed by precision comparators into digital signals (D1-D11). The threshold is at VDD/2 (=Analog-reference), regulated by the monitor channel. Monitor Channel with LED Control at Pins LEDR and LERR The analog output signal of the monitor channel is regulated by the LED current. An internal bipolar transistor sets this level to VDD/2 (control voltage at pin LEDR). Thus the signal swing of each output is symmetrical to VDD/2 (=Analog-reference) The error bit at pin LERR is triggered if the Ve of the internal bipolar transistor is larger than VDD/2. Signals Channels A0, A09 with Signal Conditioning and Self Calibration These two channels give out a sine and cosine wave which are 90 deg phase shifted. These signals have amplitudes which are almost constant due to the LED current monitoring. Due to amplifier mismatch the signals do have gain and offset errors. These errors are eliminated by an adaptive signal conditioning circuitry. The conditioning values are on-chip preprogrammed by factory. The analog output signals of A0 and A09 are supplied as true-differential voltage with a peak to peak value of 2.0 V at the pins A09P, A09N, A0P, A0N. Interpolator for Channels A0,A09 The interpolator generates the digital signals D0,D09 and D-1 to D-4. The interpolated signals D-1 to D-4 extend the 12 bit Gray code of the signals D11….D0 to form a 16 bit Gray code. D0 and D09 are digitized from A0 and A09. The channels A0A11 and A09 have very high dynamic bandwidth, which allows a real time monotone 12 bit Gray code at 12000 RPM. The interpolated 16 bit Gray code can be used up to 1000 RPM only. At more than 1000 RPM, only the 12 bit Gray code from the MSB side can be used. LSB Gray Code Correction (Pin KORR) This function block synchronizes the switching points for the 11 bit gray code of the digital signals D1 to D11 with D0 and D09 (digitized signal of A0 and A09). This Gray code correction only works for the 12 bit MSB(4096 steps per revolution). It does not work for the 4 excess interpolated bits of the 16 bit Gray code. When some special applications require code patterns other than Gray code, the Gray code correction can be disabled by putting pin KORR = 0. When that happens just the 11 data bits (D1…D11) will be sent 1:1 to the DOUT serial output. Gray code correction can be switched on or off by putting the pin KORR =1 (on) or =0 (off). MSBINV and DOUT Pins The serial interface consists of a shift register. The most significant bit, MSB (D11) will always be sent first to DOUT. The MSB can be inverted (change code direction) by using pin MSBINV. DIN and NSL Pins The Serial input DIN allows the configuration as ring register for multiple transmissions or for cascading 2 or more encoders. DIN is the input of the shift register that shifts the data to DOUT. The NSL pin controls the shift register, to switch it between load (1) or shift (0) mode. Under load mode, DOUT will give the logic of the MSB, i.e., D11. Under shift mode (0), coupled with the SCL, the register will be clocked, and gives out the serial word output bit by bit. As the clock frequency can be up to 16 MHz, the transmission of the full 16 bit word can be done within 1µs. Valid data of DOUT should be read when the SCL clock is low. Please refer to timing diagram (Figure 2). 2 Pinout Description No. 1 2 3 4 5 Pin Name NC KORR PROBE_ON PCL STCAL Digital-input Digital-Input Digital Input Positive Edge Digital Input Positive edge Negative edge Digital-Input Digital Input Digital-Input Digital-Input Positive Edge Digital Output Digital Output Digital Output Supply Voltage Gnd for supply voltage Analog output Gnd for supply voltage Analog Output Analog output Supply Voltage Analog Output Digital Output Analog Output Description Function Internally connected to cathode of LED 1 = Gray Code Correction Active Do not use Do not use To be ground Notes[1] Do not use CMOS, internal pu CMOS, internal pd CMOS, internal pu CMOS, internal pd 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 MSBINV DIN NSL SCL DOUT DO DPROBE VDD GND A09P GND A0P A09N VDDA A0N LERR LEDR 1 = MSB inverted Shift Register input. Used for cascading only Shift-register Shift (=0) / Load (=1) Control Shift-register Shift Clock Shift-Register Data Out (MSB first) DO signal DO9 signal +5 V Supply Digital GND for 5 V supply analog/digital A09 positive (+True diff.) GND for 5 V supply analog/digital A0 positive (+True diff.) A09 negative (–True diff.) +5 V Supply Analog A0 negative (–True diff.) IR-LED Current Limit Signal Do not use CMOS, internal pd CMOS, internal pd CMOS, internal pu CMOS, internal pu CMOS, 2 mA CMOS, 2 mA CMOS, 2 mA CMOS, analog out CMOS, analog out CMOS, analog out CMOS, analog out CMOS, 2 mA CMOS, analog out Note: 1. Internal pu/pd = internal pull-up (typ. 50 µA)/ pull-down (typ. 10 µA) CMOS-transistor-Rs. Pinout Configuration ESD WARNING: HANDLING PRECAUTIONS SHOULD BE TAKEN TO AVOID STATIC DISCHARGE 3 Using the AEAS-7000 VDD 0R to 2R VCC (+5V) VDD DPROBE D0 DOUT SCL min 100µ Tantal GND NSL DIN MSBINV LEDR STCAL PCL LERR PROBE_ON KORR STCAL PCL PROBE_ON KORR LERR min 2µ2 Tantal GND (C's optional) VCC GND D09 D0 DOUT SCL NSL DIN MSBINV Analogue - Outputs A09N_AREF A0P_A0 A0N_MON VDD 10R VDDA Figure 1. Schematic using AEAS-7000. Note: The RC-filter combination, especially on VDDA, is used to filter spikes and transients and is strongly recommended. It is advised that the tantalum caps be put as close to the VDD and VDDA pins as possible. It is recommended to ground the PROBE_ON pin during normal operation. Leave PCL unconnected. A09N and A0N are the negative cosine and sine waves, the negative versions of A09P and A0P. D0 is used to check the D0 signal. D0 is the digitized signal of A0. DPROBE is used to check D09, the digitized signal of A09. Recommended to be used for testing purpose only. KORR is for Gray Code correction for 12 bits resolution only. MSBINV is for user to change between counting up and counting down for a given rotating direction. MSB(D11) will always be sent out to DOUT first. LEDR, do not connect to this pin. LERR will be high when the light output of the emitter is low. This is an indicator when light intensity is at a critical stage affecting the performance of the encoder. It is caused by contamination of the codewheel or LED degradation. Operation 1) After powering up the unit using VCC = +5 V and connecting GND to ground, trigger input pins NSL and SCL using the timing diagram below (Figure 2). NSL is a control pin for the internal shift register. When triggered to low and combined with clock pulses, the serial Gray code will be shifted out to DOUT bit by bit per every clock pulse 2) The 16 bit serial gray code can then be tapped out from the pin DOUT, most significant bit (D11) first. The rate of the 16 bit Gray code serial transfer rate is dependent on the SCL clock frequency. The faster the clock, the faster the transfer rate. The maximum clock rate the AEAS-7000 can take is 16 MHz, which means the entire 16 bit Gray code can be serially transferred out in 1 µs. 3)Whenever NSL is high, the DOUT will have the logic of the MSB D11. After NSL goes low, the number of bits being trans-ferred out will depend on the number of clock pulses given to SCL. The default is 16 clock pulses for the 16 bit Gray code. If for other application where another number other than 16 is needed, just supply the corresponding number of clock pulses to the SCL, e.g., 12 bit, 13 bit, 14 bit or 15 bit, and you will get the corresponding length of Gray code words with the corresponding resolution. 4 Application - Logic A09P_APR LAPSE TIME BETWEEN WORDS, SET BY NSL 1 FRAME = 16 BITS NSL 1 SCL 2 14 15 16 DOUT(SERIAL) D11 D10 D-3 D-4 D11 Note: VALID DATA IS WHEN NSL IS LOW Figure 2. Timing diagram. Absolute Limits No. 1 2 3 4 Parameters Supply Voltage Voltages at all Input and Output Pins Operating Temperature Storage Temperature Symbol VD Vin , Vout TA TS Min. –0.3 –0.3 –25 –40 Typ. Max. 6.0 VD + 0.3 +85 +100 Units V V °C °C Operating Conditions No. 1 2 3 4 Parameters Supply Voltage Operating Temperature Input-H-Level Input-L-Level Symbol VD TA Vih Vil Min. 4.5 –25 0.7*VD 0 Typ. 5 25 Max 5.5 +85 VD 0.3*VD Units V °C V V 5 Electrical Characteristics (VD = 4.5 to 5 V, TA = –40 to +85 °C) No. Parameters Symbol Conditions Min. Typ. Max. Units Operating Currents 1 Total Current I total 25 mA Digital Inputs 1 2 Pull Down Current Pull Up Current Ipd Ipu –20 30 –5 160 µA µA Digital Outputs 1 2 Ouput-H-Level Output-L-Level Voh Vol Ioh = 2 mA Iol = –2 mA VD - 0.5 V 0 VD 0.5 V V Serial Interface 1 2 3 SCL Clock Frequency Duty Cycle Fclock Accuracy (1) fclock T clock,LH Fclock = 16 MHz Fclock = 5MHz, RPM = 80 Fsine,cos 0 0.4 ±2bits 16 0.6 MHz ns Analog-Signal-Conditioning – Signaltracks A0P, A0N,A09P,A09N 1. Signal Frequency A0, A09 Note 1: 250 KHz Accuracy would be influenced by installation control and the bearing and shaft type being used. Test conditions to determine Accuracy 1) 80 RPM 2) 25 oC, room temperature 3) At nominal radial, tangential and gap position 4) On dual preloaded bearing with absolute assembly concentricity of not exceedding 10 microns 5) SCL frequency of 5MHz 6) Both VDD & VDDA filter capacitor placed not more than 20mm from header pins 7) Tested for one revolution Mounting Consideration 24.0 12.0 ) (2x .2 Ø3 Readhead 6 Ø5 24.1 21.2 9.2 Ø42.1 0.35-0.10 (Z gap between code disc and reticle) Code Disc Ø8.02 H6 2x11 -1.27mm pitch pin header +0.15 18.85±0.2 22.6 35.1 UNLESS SPECIFIED OTHERWISE DIMENSIONS ARE IN MILLIMETRES THIRD ANGLE PROJECTION XX. XX.X XX.XX 0.3 0.1 0.03 STRIKE OUT OR FILL IN AS NEEDED Note: Codewheel mounting tolerances for radial, tangential and Z gap are: Radial: ±50 um Tangential: ±40 um Z Gap: ±50 um 3.65 1.5 Plug & Play Hub-Shaft design The following details the design of the hub-shaft of which the dimensions must be strictly followed for the plug & play feature of the AEAS-7000 to work. In order to secure the code disk to the hub, an adhesive must be utilised. Agilent recommends using DELODUOPOX, 1895 from DELO. Stainless steel is recommended as the hub-shaft material. 58 Ordering Information A complete instruction for AEAS-7000 Plug & Play installation consideration can be found in AEAS-7000 application note. AEA - 7000 - 1 G S 0 S - Standard (-25°C to +85°C) Legend 1 = 5V G = gray code S = serial output mode Ø18 +0 Ø8.02h6(- 0.01) D - 13 bits G - 16 bits 0.8 depth as adhesive reservoir Ø16 0.01 Ø15 Ø10h6(+0 ) - 0.01 2 20 1 Motor end is user specified Ø12 12 4.2 -0 A Ø0.01 +0.03 Ø11 0.01 A 0.02 0.01 A 0.02 Straightness Flatness Perpendicularity Total Run-out www.agilent.com/semiconductors For product information and a complete list of distributors, please go to our web site. For technical assistance call: Americas/Canada: +1 (800) 235-0312 or (916) 788-6763 Europe: +49 (0) 6441 92460 China: 10800 650 0017 Hong Kong: (+65) 6756 2394 India, Australia, New Zealand: (+65) 6755 1939 Japan: (+81 3) 3335-8152 (Domestic/International), or 0120-61-1280 (Domestic Only) Korea: (+65) 6755 1989 Singapore, Malaysia, Vietnam, Thailand, Philippines, Indonesia: (+65) 6755 2044 Taiwan: (+65) 6755 1843 Data subject to change. Copyright © 2004 Agilent Technologies, Inc. February 23, 2004 5988-9627EN