A S5 3 11 H i g h R e s o l u t i o n M a g n e t i c L i n e a r E n co d er 1 General Description The AS5311 is available in a PB-free TSSOP-20 package and qualified for an ambient temperature range from -40°C to +125°C. The AS5311 is a contactless high resolution magnetic linear encoder for accurate linear motion and off-axis rotary sensing with a resolution down to <0.5µm. It is a system-on-chip, combining integrated Hall elements, analog front end and digital signal processing on a single chip, packaged in a small 20-pin TSSOP package. 2 Key Features Two 12-bit digital absolute outputs: - Serial interface and - Pulse width modulated (PWM) output Incremental output with Index A multi-pole magnetic strip or ring with a pole length of 1.0mm is required to sense the rotational or linear motion. The magnetic strip is placed above the IC at a distance of typ. 0.3mm. The absolute measurement provides instant indication of the magnet position within one pole pair with a resolution of 488nm per step (12bit over 2.0mm). This digital data is available as a serial bit stream and as a PWM signal. “Red-Yellow-Green” indicators monitor magnet placement over the chip 3 Applications Furthermore, an incremental output is available with a resolution of 1.95µm per step. An index pulse is generated once for every pole pair (once per 2.0mm).The travelling speed in incremental mode is up to 650mm/second. Micro-Actuator An internal voltage regulator allows the AS5311 to operate at either 3.3 V or 5 V supplies. Depending on the application the AS5311 accepts multi-pole strip magnets as well as multi-pole ring magnets, both radial and axial magnetized (see Figure 1 and Figure 3). Replacement feedback Servo drive feedback Robotics of optical encoders Figure 1. AS5311 Block Diagram VDD3V3 VDD5V MagINCn MagDECn LDO 3.3V PWM Interface Sin Linear Hall Array & Frontend Amplifier AS5311 Cos PWM Ang DSP Mag Absolute Interface (SSI) DO CSn CLK OTP Register Programming Parameters Incremental Interface A B Index Prog www.ams.com/AS5311 Revision 1.12 1 - 29 AS5311 Datasheet - C o n t e n t s Contents 1 General Description .................................................................................................................................................................. 1 2 Key Features............................................................................................................................................................................. 1 3 Applications............................................................................................................................................................................... 1 4 Pin Assignments ....................................................................................................................................................................... 3 4.1 Pin Descriptions.................................................................................................................................................................................... 3 5 Absolute Maximum Ratings ...................................................................................................................................................... 5 6 Electrical Characteristics........................................................................................................................................................... 6 6.1 Operating Conditions............................................................................................................................................................................ 6 6.2 DC Characteristics for Digital Inputs and Outputs ................................................................................................................................ 6 6.2.1 6.2.2 6.2.3 6.2.4 CMOS Schmitt-Trigger Inputs: CLK, CSn (CSn = internal Pull-up) ............................................................................................. CMOS Output Open Drain: MagINCn, MagDECn ....................................................................................................................... CMOS Output: PWM ................................................................................................................................................................... Tristate CMOS Output: DO.......................................................................................................................................................... 6.3 Magnetic Input Specification................................................................................................................................................................. 6 6 6 7 7 6.4 Electrical System Specifications........................................................................................................................................................... 8 6.5 Timing Characteristics .......................................................................................................................................................................... 9 6.5.1 Pulse Width Modulation Output ................................................................................................................................................... 9 7 Detailed Description................................................................................................................................................................ 10 7.1 Incremental Outputs ........................................................................................................................................................................... 11 7.1.1 Incremental Power-up Lock Option ........................................................................................................................................... 11 7.2 Incremental Output Hysteresis ........................................................................................................................................................... 12 7.3 Synchronous Serial Interface (SSI) .................................................................................................................................................... 12 7.4 Absolute Output Jitter and Hysteresis ................................................................................................................................................ 14 7.4.1 Adding a Digital Hysteresis........................................................................................................................................................ 14 7.4.2 Implementing Digital Filtering .................................................................................................................................................... 14 7.5 Z-axis Range Indication (“Red/Yellow/Green” Indicator) .................................................................................................................... 14 7.6 Pulse Width Modulation (PWM) Output.............................................................................................................................................. 15 7.7 3.3V / 5V Operation............................................................................................................................................................................ 16 8 Application Information ........................................................................................................................................................... 18 8.1 Magnetization ..................................................................................................................................................................................... 19 8.2 Position of the Index Pulse................................................................................................................................................................. 19 8.3 Mounting the Magnet.......................................................................................................................................................................... 20 8.3.1 Vertical Distance........................................................................................................................................................................ 20 8.3.2 Alignment of Multi-pole Magnet and IC...................................................................................................................................... 20 8.3.3 Lateral Stroke of Multi-pole Strip Magnets................................................................................................................................. 20 8.4 Measurement Data Example.............................................................................................................................................................. 8.5 AS5311 Off-axis Rotary Applications.................................................................................................................................................. 9 Package Drawings and Markings ........................................................................................................................................... www.ams.com/AS5311 Revision 1.12 23 25 9.1 Recommended PCB Footprint............................................................................................................................................................ 10 Ordering Information............................................................................................................................................................. 22 26 28 2 - 29 AS5311 Datasheet - P i n A s s i g n m e n t s 4 Pin Assignments Figure 2. Pin Assignments (Top View) NC 20 NC MagIncn 2 19 VDD5V MagDecn 3 18 VDD3V3 A 4 17 NC B 5 16 NC NC 6 15 PWM Index 7 14 CSn VSS 8 13 CLK Prog 9 12 DO NC 10 11 NC AS5311 1 4.1 Pin Descriptions Pin 4(A), 5(B) and 7(Index) are the incremental outputs. The incremental output has a resolution of 10-bit per pole pair, resulting in a step length of 1.95µm. Note: Pin 14 (CSn) must be low to enable the incremental outputs. Pins 12, 13 and 14 are used for serial data transfer. Chip Select (CSn; active low) initiates serial data transfer. CLK is the clock input and DO is the data output. A logic high at CSn puts the data output pin (DO) to tri-state and terminates serial data transfer. CSn must be low to enable the incremental outputs. See Section 7.1.1 for further options. Pin 8 is the supply ground pin. Pins 18 and 19 are the positive supply pins. For 5V operation, connect the 5V supply to pin 19 and add a 2µF…10µF buffer capacitor at pin 18. For 3.3V operation, connect both pins 18 and 19 to the 3.3V supply. Pin 9 is used for factory programming only. It should be connected to VSS. Pins 2 and 3 are the magnetic field change indicators, MagINCn and MagDECn (magnetic field strength increase or decrease through variation of the distance between the magnet and the device). These outputs can be used to detect the valid magnetic field range. External pull-up resistors are required at these pins. See Section 6.2.2 for maximum output currents on these pins. Since they are open-drain outputs they can also be combined (wired-and). Pin 15 (PWM) allows a single wire output of the 12-bit absolute position value within one pole pair (2.0mm). The value is encoded into a pulse width modulated signal with 1µs pulse width per step (1µs to 4097µs over one pole pair). Pins 1, 6, 10, 11, 16, 17 and 20 are for internal use and must not be connected. www.ams.com/AS5311 Revision 1.12 3 - 29 AS5311 Datasheet - P i n A s s i g n m e n t s Table 1. Pin Descriptions Pin Number Pin Name Pin Type 1 NC - 2 MagINCn 3 MagDECn 4 A 5 B 6 NC - Must be left unconnected 7 Index Digital output Incremental output Index 8 VSS Supply pin 9 Prog 10 NC - Must be left unconnected 11 NC - Must be left unconnected 12 DO Digital output /tri-state Data Output of Synchronous Serial Interface 13 CLK Digital input, Clock Input of Synchronous Serial Interface; Schmitt-Trigger input Schmitt-Trigger input 14 CSn Digital input pull-up, Chip Select, active low; Schmitt-Trigger input, internal pull-up resistor (~50kW). Schmitt-Trigger input Must be low to enable incremental outputs 15 PWM Digital output 16 NC - Must be left unconnected 17 NC - Must be left unconnected 18 VDD3V3 19 VDD5V 20 NC www.ams.com/AS5311 Digital output open drain Digital output Description Must be left unconnected Indicates “Red/Yellow/Green Range” depending on the distance between device and magnet Indicates “Red/Yellow/Green Range” depending on the distance between device and magnet Incremental output A Incremental output B Negative Supply Voltage (GND) Digital input pull-down OTP Programming Input for factory programming. Connect to VSS. Supply pin Pulse Width Modulation of approx. 244Hz; 1µs/step 3V-Regulator output; internally regulated from VDD5V. Connect to VDD5V for 3V supply voltage. Do not load externally. Positive Supply Voltage, 3.0 to 5.5 V - Must be left unconnected Revision 1.12 4 - 29 AS5311 Datasheet - A b s o l u t e M a x i m u m R a t i n g s 5 Absolute Maximum Ratings Stresses beyond those listed in Table 2 may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in Electrical System Specifications on page 8 is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 2. Absolute Maximum Ratings Parameter Min Max Units DC supply voltage at pin VDD5V -0.3 7 V 5 V DC supply voltage at pin VDD3V3 Comments Input pin voltage -0.3 VDD5V +0.3 V Except VDD3V3 Input current (latchup immunity) -100 100 mA Norm: JEDEC 78 ±2 kV Norm: MIL 883 E method 3015 125 °C Min – 67°F; Max +257°F 260 °C The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/ JEDEC J-STD-020C “Moisture/Reflow Sensitivity Classification for Non-Hermetic Solid State Surface Mount Devices”. The lead finish for Pb-free leaded packages is matte tin (100% Sn). 85 % Electrostatic discharge Storage temperature -55 Body temperature (Lead-free package) Humidity non-condensing Moisture Sensitive Level (MSL) www.ams.com/AS5311 5 Represents a maximum floor time of 168h 3 Revision 1.12 5 - 29 AS5311 Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s 6 Electrical Characteristics TAMB = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation), unless otherwise noted. 6.1 Operating Conditions Table 3. Operating Conditions Symbol Parameter Note Min TAMB Ambient temperature -40°F +257°F -40 Isupp Supply current VDD5V VDD3V3 Supply voltage at pin VDD5V Voltage regulator output voltage at pin VDD3V3 5V Operation VDD5V VDD3V3 Supply voltage at pin VDD5V Supply voltage at pin VDD3V3 3.3V Operation (pin VDD5V and VDD3V3 connected) Typ Max Units 125 °C 16 21 mA 4.5 3.0 5.0 3.3 5.5 3.6 V V 3.0 3.0 3.3 3.3 3.6 3.6 V V 6.2 DC Characteristics for Digital Inputs and Outputs 6.2.1 CMOS Schmitt-Trigger Inputs: CLK, CSn (CSn = internal Pull-up) Table 4. CMOS Schmitt-Trigger Inputs Symbol Parameter Conditions Min VIH High level input voltage Normal operation 0.41 * VDD5V VIL Low level input voltage VIon - VIoff Schmitt Trigger hysteresis ILEAK IiL Input leakage current Pull-up low level input current 6.2.2 Typ Max Units V 0.13 * VDD5V 1 V V CLK only -1 1 CSn only, VDD5V: 5.0V -30 -100 µA CMOS Output Open Drain: MagINCn, MagDECn Table 5. CMOS Output Open Drain Symbol Parameter VOL Low level output voltage IO Output current IOZ Open drain leakage current 6.2.3 Conditions Min Typ Max Units VSS+0.4 V VDD5V: 4.5V 4 VDD5V: 3V 2 mA 1 µA Max Units CMOS Output: PWM Table 6. CMOS Output Symbol Parameter VOH High level output voltage VOL Low level output voltage IO Output current www.ams.com/AS5311 Conditions Min Typ VDD5V-0.5 V VSS+0.4 VDD5V: 4.5V 4 VDD5V: 3V 2 Revision 1.12 V mA 6 - 29 AS5311 Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s 6.2.4 Tristate CMOS Output: DO Table 7. Tristate CMOS Output Symbol Parameter VOH High level output voltage VOL Low level output voltage IO Output current Conditions Min Typ Max Units VDD5V -0.5 V VSS+0.4 VDD5V: 4.5V 4 VDD5V: 3V 2 V mA 6.3 Magnetic Input Specification Two-pole cylindrical diametrically magnetized source: Table 8. Magnetic Input Specification Symbol Parameter Note Lp Pole length tmag Pole pair length Recommended magnet: plastic or rubber bonded ferrite or NdFeB Bpk Magnetic input field amplitude Required vertical component of the magnetic field strength on the die’s surface Boff Magnetic offset Btc Min Typ Max Units 1 mm 2 mm 40 mT Constant magnetic stray field ±5 mT Magnetic field temperature drift Recommended magnet: plastic or rubber bonded ferrite or NdFeB 0.2 %/K Magnetic input field variation Including offset gradient ±2 % Vabs Linear travelling speed Incremental output: 1024 steps / polepair 1 including interpolation 650 mm/ sec Disp Displacement Maximum shift between defined Hall sensor center and magnet centerline; depends on magnet geometries 0.5 mm ZDist Vertical gap Package to magnet surface; depends on magnet strength 0.3 mm Plastic or rubber bonded Ferrite -0.19 Plastic or rubber bonded Neodymium (NdFeB) -0.12 Recommended magnet material and temperature drift 10 %/K 1. 1) For absolute outputs, a practical speed limit is 2345 mm/s. At higher speeds, input signal cancellation will occur and the detected field decreases due to the internal front-end. Significant signal change is indicated by the status bits. 2) With increasing speed, the distance between two samples increases. The travelling distance between two subsequent samples can be calculated as: v sampling – dist = ---fs where: sampling_distance = travelling distance between samples (in mm) v = travelling speed (in mm/sec) fs = sampling rate in Hz (see Table 9) www.ams.com/AS5311 Revision 1.12 7 - 29 AS5311 Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s 6.4 Electrical System Specifications Table 9. Electrical System Specifications Symbol Parameter Note RESabs Resolution, absolute outputs 0.488 um/step (12bit / 2mm pole pair) 12 bit / polepair RESinc Resolution, incremental outputs 1.95 um/step (10bit / 2mm pole pair) 10 bit / polepair INLopt Integral non-linearity (optimum) Maximum error with respect to the best line fit. Ideal magnet TAMB =25 °C. ± 5.6 μm INLtemp Integral non-linearity (over temperature) Maximum error with respect to the best line fit. Ideal magnet Tamb = -30 to +70 °C. ± 10 μm DNL Differential non-linearity 10bit, no missing codes ± 0.97 μm TN Transition noise 1 sigma 0.6 μm RMS Von Power-on reset thresholds: On voltage; 300mV typ. hysteresis Voff Power-on reset thresholds: Off voltage; 300mV typ. hysteresis Min Typ Max 1.37 2.2 2.9 1.08 1.9 2.6 DC supply voltage 3.3V (VDD3V3) Units V tPwrUp Power-up time Until status bit OCF = 1 20 ms tdelay System propagation delay absolute output Delay of ADC, DSP and absolute interface 96 µs System propagation delay incremental Including interpolation delay at high speeds output 384 µs tdelay TAMB = 25°C 9.90 10.42 10.94 TAMB = -40 to +125°C, 9.38 10.42 11.46 fS Internal sampling rate for absolute output Hyst Hysteresis, incremental outputs No Hysteresis at absolute serial outputs Read-out frequency Maximum clock frequency to read out serial data CLK 2 kHz LSB 1 MHz Notes: 1. Integral Non-Linearity (INL) is the maximum deviation between actual position and indicated position. 2. Differential Non-Linearity (DNL) is the maximum deviation of the step length from one position to the next. 3. Transition Noise (TN) is the repeatability of an indicated position. www.ams.com/AS5311 Revision 1.12 8 - 29 AS5311 Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s 6.5 Timing Characteristics Table 10. Synchronous Serial Interface (SSI) Symbol Parameter Note tDOactive Data output activated (logic high) Time between falling edge of CSn and data output activated tCLKFE First data shifted to output register Time between falling edge of CSn and first falling edge of CLK 500 ns TCLK / 2 Start of data output Rising edge of CLK shifts out one bit at a time 500 ns tDOvalid Data output valid Time between rising edge of CLK and data output valid 413 ns tDOtristate Data output tristate After the last bit DO changes back to “tristate” 100 ns tCSn Pulse width of CSn CSn = high; To initiate read-out of next angular position 500 fCLK Read-out frequency Clock frequency to read out serial data >0 Note Min Signal period = 4098µs ±5% at TAMB = 25°C 6.5.1 Min Typ Max Units 100 ns ns 1 MHz Typ Max Units 232 244 256 Signal period = 4098µs ±10% at TAMB = -40 to +125°C 220 244 268 Pulse Width Modulation Output Table 11. Pulse Width Modulation Output Symbol f PWM Parameter PWM frequency Hz PW MIN Minimum pulse width Position 0d = 0µm 0.9 1 1.1 µs PW MAX Maximum pulse width Position 4095d = 1999.5µm 3892 4097 4301 µs www.ams.com/AS5311 Revision 1.12 9 - 29 AS5311 Datasheet - D e t a i l e d D e s c r i p t i o n 7 Detailed Description The different types of outputs relative to the magnet position are outlined in Figure 3 below. The absolute serial output counts from 0….4095 within one pole pair and repeats with each subsequent pole pair. Likewise, the PWM output starts with a pulse width of 1µs, increases the pulse width with every step of 0.488µm and reaches a maximum pulse width of 4097µs at the end of each pole pair. An index pulse is generated once for every pole pair. 256 incremental pulses are generated at each output A and B for every pole pair. The outputs A and B are phase shifted by 90 electrical degrees, which results in 1024 edges per pole pair. As the incremental outputs are also repeated with every pole pair, a constant train of pulses is generated as the magnet moves over the chip. Figure 3. AS5311 Outputs Relative to Magnet Position 2mm S N S N S N S N S N S N absolute output : 0 … .. 4095 0 … .. 4095 0 … .. 4095 0 … .. 4095 0 … .. 4095 0 … .. 4095 PWM output : 1 … . 4097µs A : 256 B : 256 pulses / polepair pulses / polepair A + B = 1024 steps / polepair Index : 1 pulse / polepair www.ams.com/AS5311 Revision 1.12 10 - 29 AS5311 Datasheet - D e t a i l e d D e s c r i p t i o n 7.1 Incremental Outputs Figure 4 shows the two-channel quadrature output of the AS5311. Output A leads output B when the magnet is moving from right to left and output B leads output A when the magnet is moving from left to right(see Figure 14). Figure 4. Incremental Outputs Incremental outputs Mechanical Zero Position Movement Direction Change Mechanical Zero Position A B Index=0 1LSB Index Movement right to left CSn Hyst = 2 LSB Movement left to right tIncremental outputs valid 7.1.1 Incremental Power-up Lock Option After power-up, the incremental outputs can optionally be locked or unlocked, depending on the status of the CSn pin: CSn = low at power-up: CSn has an internal pull-up resistor and must be externally pulled low (Rext ≤ 5kΩ). If Csn is low at power-up, the incremental outputs A, B and Index will be high until the internal offset compensation is finished. This unique state may be used as an indicator for the external controller to shorten the waiting time at power-up. Instead of waiting for the specified maximum power up-time (see Electrical System Specifications on page 8), the controller can start requesting data from the AS5311 as soon as the state (A= B= Index = high) is cleared. CSn = high or open at power-up: In this mode, the incremental outputs (A, B, Index) will remain at logic high state after power-up, until CSn goes low or a low pulse is applied at CSn and internal offset compensation is finished. This mode allows intentional disabling of the incremental outputs after power-up until for example the system microcontroller is ready to receive data. Once the incremental outputs are unlocked they can not be disabled during operation. www.ams.com/AS5311 Revision 1.12 11 - 29 AS5311 Datasheet - D e t a i l e d D e s c r i p t i o n 7.2 Incremental Output Hysteresis Figure 5. Hysteresis Illustration Incremental Output Indication X +4 Hysteresis: 2 steps X +3 X +2 X +1 X X Magnet Position X +1 X +2 X +3 X +4 X +5 Movement left --> right Movement right --> left To avoid flickering incremental outputs at a stationary magnet position, a hysteresis is introduced. In case of a movement direction change, the incremental outputs have a hysteresis of 2 LSB. For constant movement directions, every magnet position change is indicated at the incremental outputs (see Figure 4). If for example the magnet moves from position “x+3” to “x+4”, the incremental output would also indicate this position accordingly. A change of the magnet’s movement direction back to position “x+3” means, that the incremental output still remains unchanged for the duration of 2 LSB, until position “x+2” is reached. Following this movement, the incremental outputs will again be updated with every change of the magnet position. 7.3 Synchronous Serial Interface (SSI) The Serial interface allows data transmission of the 12-bit absolute linear position information (within one pole pair = 2.0mm). Data bits D11:D0 represent the position information with a resolution of 488nm (2000µm / 4096) per step. CLK must be high at the falling edge of CSn. Figure 6. Synchronous Serial Interface with Absolute Angular Position Data tCLK FE CSn tCLK FE TCLK/2 tCSn 1 CLK DO 8 D11 tDO active www.ams.com/AS5311 D10 D9 D8 D7 D6 D5 18 D4 D3 D2 D1 D0 OCF COF LIN Mag INC tDO valid Angular Position Data Status Bits Revision 1.12 Mag DEC 1 Even PAR D11 tDO Tristate 12 - 29 AS5311 Datasheet - D e t a i l e d D e s c r i p t i o n If CLK is low at the falling edge of CSn, the first 12 bits represent the magnitude information, which is proportional to the magnetic field strength. This information can be used to detect the presence and proper distance of the magnetic strip by comparing it to a known good value (depends on the magnet material and distance). The automatic gain control (AGC) maintains a constant MAGnitude value of 3F hex (=“green” range). If the MAG value is <>3F hex, the AGC is out of the regulating range (“yellow” or “red” range). See Table 13 for more details. For AGC algorithm only M11: M4 of the magnitude are used. A value of zero or close to zero indicates a missing magnet. Figure 7. Synchronous Serial Interface with Magnetic Field Strength Data tCLK FE CSn TCLK/2 tCSn 1 CLK DO M11 8 M10 M9 M8 M7 M6 M5 M4 18 M3 M2 M1 M0 OCF COF LIN Mag INC Mag DEC tDO valid tDO active Magnetic field strength data Status Bits 1 Even PAR D11 tDO Tristate If CSn changes to logic low, Data Out (DO) will change from high impedance (tri-state) to logic high and the read-out will be initiated. After a minimum time tCLK FE, data is latched into the output shift register with the first falling edge of CLK. Each subsequent rising CLK edge shifts out one bit of data. The serial word contains 18 bits, if CLK is high at the falling edge of CSn (see Figure 6), the first 12 bits are the absolute distance information D[11:0], the subsequent 6 bits contain system information, about the validity of data such as OCF, COF, LIN, Parity and Magnetic Field status (increase/decrease). If CLK is low at the falling edge of CSn, the first 12 bits contain the magnitude information and the subsequent bits contain the status bits (see Figure 7). A subsequent measurement is initiated by a “high” pulse at CSn with a minimum duration of tCSn. Data Contents: D11:D0 absolute linear position data (MSB is clocked out first) M11:M0 magnitude / magnetic field strength information (MSB is clocked out first) OCF (Offset Compensation Finished), logic high indicates the finished Offset Compensation Algorithm. If this bit is not set, the data at D11:D0 (likewise M11:M0) may be invalid. COF (Cordic Overflow), logic high indicates an out of range error in the CORDIC part. When this bit is set, the data at D11:D0 (likewise M11:M0) is invalid. This alarm may be resolved by bringing the magnet within the X-Y-Z tolerance limits. LIN (Linearity Alarm), logic high indicates that the input field generates a critical output linearity. When this bit is set, the data at D11:D0 may still be used, but can contain invalid data. This warning can be resolved by increasing the magnetic field strength. Even Parity bit for transmission error detection of bits 1…17 (D11…D0, OCF, COF, LIN, MagINC, MagDEC) www.ams.com/AS5311 Revision 1.12 13 - 29 AS5311 Datasheet - D e t a i l e d D e s c r i p t i o n Data D11:D0 is valid, when the status bits have the following configurations: Table 12. Status Bit Outputs OCF COF 1 LIN 0 0 MagINC MagDEC 0 0 0 1 1 0 1* 1* Parity Even checksum of bits 1:17 *MagInc=MagDec=1 is only recommended in YELLOW mode (see Table 13). 7.4 Absolute Output Jitter and Hysteresis Note: There is no hysteresis or additional filtering at the absolute output. This allows a determination of the magnet’s absolute position within one pole pair down to submicron range. Due to the intentionally omitted hysteresis and due to noise (e.g. from weak magnetic fields), the absolute output may jitter when the magnet is stationary over the chip. In order to get a stable 12-bit absolute reading, two common methods may be implemented to reduce the jitter. 7.4.1 Adding a Digital Hysteresis The hysteresis feature of the incremental outputs is described in Incremental Output Hysteresis. An equivalent function can be implemented in the software of the external microcontroller. The hysteresis should be larger than the peak-to-peak noise (=jitter) of the absolute output in order to mask it and create a stable output reading. Note: The 2-bit hysteresis on the incremental output (=3.9µm) is equivalent to a hysteresis of 8LSB on the absolute output. 7.4.2 Implementing Digital Filtering Another useful alternative or additional method to reduce jitter is digital filtering. This can be accomplished simply by averaging, for example a moving average calculation in the external microcontroller. Averaging 4 readings results in 6dB (=50%) noise and jitter reduction. An average of 16 readings reduces the jitter by a factor of 4. Averaging causes additional latency of the processed data. Therefore it may be useful to adjust the depth of averaging depending on speed of travel. For example using a larger depth when the magnet is stationary and reducing the depth when the magnet is in motion. 7.5 Z-axis Range Indication (“Red/Yellow/Green” Indicator) The AS5311 provides several options of detecting the magnet distance by indicating the strength of the magnetic field. The signal indicator pins MagINCn and MagDECn are available as hardware pins (pins 2 and 3) and display the “Red/Yellow/Green Range”. Additionally, the serial data stream (see Figure 6) offers the MagINC, MagDEC and LIN status bits. The LIN status bit indicates the nonrecommended “red” range. The MAGnitude register provides additional information about the strength of the magnetic field (see Figure 7). For Zaxis Range Indication only M11:M4 of the magnitude are used. The digital status bits MagINC, MagDec, LIN and the hardware pins MagINCn, MagDECn have the following function: Table 13. Magnetic Field Strength Red-Yellow-Green Indicators Status Bits MagINC MagDEC MAG LIN Hardware Pins 1 M11…M4 MagINCn MagDECn Description 0 0 0 3F hex Off Off No distance change Magnetic input field OK (GREEN range, ~10…40mT peak amplitude) 0 1 0 3F hex Off Off Distance increase; this state is a dynamic state and only active while the magnet is moving away from the chip. Magnitude register may change but regulates back to 3F hex. 1 0 0 3F hex Off Off Distance decrease; this state is a dynamic state and only active while the magnet is moving towards the chip. Magnitude register may change but regulates back to 3F hex. www.ams.com/AS5311 Revision 1.12 14 - 29 AS5311 Datasheet - D e t a i l e d D e s c r i p t i o n Table 13. Magnetic Field Strength Red-Yellow-Green Indicators Status Bits MagINC MagDEC MAG LIN Hardware Pins 1 M11…M4 MagINCn MagDECn Description 1 1 0 20 hex5F hex On Off YELLOW range: magnetic field is ~3.4…54.5mT. The AS5311 may still be operated in this range, but with slightly reduced accuracy. 1 1 1 <20 hex >5F hex On On RED range: magnetic field is <3.4mT (MAG <20) or >54.5mT (MAG >5F). It is still possible to operate the AS5311 in the red range, but not recommended. n/a n/a Not available All other combinations 1. Pin 2 (MagINCn) and Pin 3 (MagDECn) 7.6 Pulse Width Modulation (PWM) Output The AS5311 provides a pulse width modulated output (PWM), whose duty cycle is proportional to the relative linear position of the magnet within one pole pair (2.0mm). This cycle repeats after every subsequent pole pair: (EQ 1) Position = ton ⋅ 4098 (ton + toff ) − 1 for digital position = 0 – 4094 Exception: A linear position of 1999.5µm = digital position 4095 will generate a pulse width of ton = 4097µs and a pause toff = 1µs The PWM frequency is internally trimmed to an accuracy of ±5% (±10% over full temperature range). This tolerance can be cancelled by measuring the complete duty cycle as shown above. www.ams.com/AS5311 Revision 1.12 15 - 29 AS5311 Datasheet - D e t a i l e d D e s c r i p t i o n Figure 8. PWM Output Signal Position PW MIN 0µm (Pos 0) 1µs 4098 µs PW MAX 1999.5µm (Pos 4095) 409 7 µs 1/f PWM 7.7 3.3V / 5V Operation The AS5311 operates either at 3.3V ±10% or at 5V ±10%. This is made possible by an internal 3.3V Low-Dropout (LDO) Voltage regulator. The internal supply voltage is always taken from the output of the LDO, meaning that the internal blocks are always operating at 3.3V. For 3.3V operation, the LDO must be bypassed by connecting VDD3V3 with VDD5V (see Figure 9). For 5V operation, the 5V supply is connected to pin VDD5V, while VDD3V3 (LDO output) must be buffered by a 2.2...10µF capacitor, which is supposed to be placed close to the supply pin. The VDD3V3 output is intended for internal use only. It must not be loaded with an external load. The output voltage of the digital interface I/O’s corresponds to the voltage at pin VDD5V, as the I/O buffers are supplied from this pin. A buffer capacitor of 100nF is recommended in both cases close to pin VDD5V. Note that pin VDD3V3 must always be buffered by a capacitor. It must not be left floating, as this may cause an instable internal 3.3V supply voltage which may lead to larger than normal jitter of the measured angle. www.ams.com/AS5311 Revision 1.12 16 - 29 AS5311 Datasheet - D e t a i l e d D e s c r i p t i o n Figure 9. Connections for 5V and 3.3V Supply Voltages 5 V Operation 3. 3 V Operation 2.2 ... 10 µF VDD3V3 VDD 3 V 3 100 n VDD5V 4. 5 - 5. 5 V Prog LDO 100 n Internal VDD VDD 5 V DO 3. 0 - 3. 6 V CLK CSn A B Prog Index VSS I N T E R F A C E DO CLK CSn A B Index VSS AS5311 www.ams.com/AS5311 Internal VDD PWM PWM I N T E R F A C E LDO AS5311 Revision 1.12 17 - 29 AS5311 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 8 Application Information Figure 10. AS5311 with Multi-pole Magnetic Strip for Linear Motion Sensing Figure 11. AS5311 with Multi-pole Ring Magnets for Off-axis Rotary Motion Sensing www.ams.com/AS5311 Revision 1.12 18 - 29 AS5311 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 8.1 Magnetization The AS5311 accepts magnetic multi-pole strip or ring magnets with a pole length of 1.0mm. Recommended magnet materials include plastic or rubber bonded ferrite or Neodymium magnets. It is not recommended to use the AS5311 with other pole lengths as this will create additional non-linearities. Figure 12. Additional Error from Pole Length Mismatch AS5311 Systematic Linearity Error Caused by Pole Length Deviation 70.00 60.00 Error [µm] 50.00 Error [µm] 40.00 30.00 20.00 10.00 0.00 750 800 850 900 950 1000 1050 1100 1150 1200 1250 Pole Length [µm] Figure 12 shows the error caused by a mismatch of pole length. Note that this error is an additional error on top of the chip-internal INL and DNL errors (see Electrical System Specifications on page 8). For example, when using a multi-pole magnet with 1.2mm pole length instead of 1.0mm, the AS5311 will provide 1024 incremental steps or 4096 absolute positions over 2.4mm, but with an additional linearity error of up to 50µm. The curvature of ring magnets may cause linearity errors as well due to the fact that the Hall array on the chip is a straight line while the poles on the multi-pole ring are curved. These errors decrease with increasing ring diameter. It is therefore recommended to keep the ring diameter measured at the location of the Hall array at 20mm or higher. 8.2 Position of the Index Pulse An index pulse is generated when the North and South poles are placed over the Hall array as shown in Figure 14. The incremental output count increases when the magnet is moving to the left, facing the chip with pin#1 at the lower left corner (see Figure 14 top drawing). At the same time, the absolute position value increases. Likewise, the position value decreases when the magnet is moved in the opposite direction. www.ams.com/AS5311 Revision 1.12 19 - 29 AS5311 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 8.3 Mounting the Magnet 8.3.1 Vertical Distance As a rule of thumb, the gap between chip and magnet should be ½ of the pole length, that is Z=0.5mm for the 1.0mm pole length of the AS5311 magnets. However, the gap also depends on the strength of the magnet. Typical gaps for AS5311 magnets range from 0.3 to 0.6mm (see Electrical System Specifications on page 8). The AS5311 automatically adjusts for fluctuating magnet strength by using an automatic gain control (AGC). The vertical distance should be set such that the AS5311 is in the “green” range. See Z-axis Range Indication (“Red/Yellow/Green” Indicator) on page 14 for more details. 8.3.2 Alignment of Multi-pole Magnet and IC When aligning the magnet strip or ring to the AS5311, the centerline of the magnet strip should be placed exactly over the Hall array. A lateral displacement in Y-direction (across the width of the magnet) is acceptable as long as it is within the active area of the magnet. See Figure 14 for the position of the Hall array relative to Pin #1. Note: The active area in width is the area in which the magnetic field strength across the width of the magnet is constant with reference to the centerline of the magnet (see Figure 13). 8.3.3 Lateral Stroke of Multi-pole Strip Magnets The lateral movement range (stroke) is limited by the area at which all Hall sensors of the IC are covered by the magnet in either direction. The Hall array on the AS5311 has a length of 2.0mm, hence the total stroke is, maximum lateral Stroke = Length of active area – length of Hall array (EQ 2) Note: Active area in length is defined as the area containing poles with the specified 1.0mm pole length. Shorter poles at either edge of the magnet must be excluded from the active area (see Figure 13). B pk B pk Figure 13. Active Area of Strip Magnet Active Area Active area ( length ) A c ti v e a r e a ( wi dt h) B N 2 mm www.ams.com/AS5311 S N S N S N S N S recommended scanning path strip length Revision 1.12 20 - 29 AS5311 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Figure 14. Alignment of Magnet Strip with AS5311 Sensor IC position value increases leftmost magnet position Die C/L S N S N S N S N S N AS5311 Package Outline position value decreases rightmost magnet position S N 1.00 1.00 S N S N S N S N 2.576±0.235 3.200±0.235 Die C/L 3.035±0.235 0.245 ± 0.100 vertical airgap magnet strip carrier see text 0.755 ± 0.100 www.ams.com/AS5311 Revision 1.12 Note: all dimensions in mm 21 - 29 AS5311 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 8.4 Measurement Data Example Figure 15 shows typical test results of the accuracy obtained by a commercially available multi-pole magnetic strip. The graph shows the accuracy over a stroke of 8mm at two different vertical gaps, 0.2mm and 0.4mm. As displayed, the accuracy is virtually identical (about ±10µm) for both airgaps due to the automatic gain control of the AS5311 which compensates for airgap changes. The accuracy depends greatly on the length and strength of each pole and hence from the precision of the tool used for magnetization as well as the homogeneity of the magnet material. As the error curve in the example below does not show a repetitive pattern for each pole pair (each 2.0mm), this is most likely an indication that the pole lengths of this particular sample do not exactly match. While the first pole pair (0...2mm) shows the greatest non-linearities, the second pole (2…4mm) is very precise, etc. Figure 15. Sample Test Results of INL at Different Airgaps 25 INL MS10-10 20 z= 200µ z= 400µ 15 Error [µm] 10 5 0 -5 -10 -15 -20 -25 0 1000 2000 3000 4000 5000 6000 7000 8000 X [µm] Note: The magnet sample used in Figure 15 is a 10-pole plastic bonded ferrite magnet as shown in Figure 13. The corresponding magnet datasheet (MS10-10) is available for download from the ams website, magnet samples can be ordered from the ams online web shop. www.ams.com/AS5311 Revision 1.12 22 - 29 AS5311 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 8.5 AS5311 Off-axis Rotary Applications The AS5311 can also be used as an off-axis rotary encoder, as shown in Figure 11. In such applications, the multi-pole magnetic strip is replaced by a multi-pole magnetic ring. The ring can have radial or axial magnetization. Figure 16. Angular Resolution and Maximum Speed vs. Ring Diameter AS5311 off-axis rotary resolution & speed 700 160000 resolution 140000 600 120000 500 100000 400 80000 300 60000 200 40000 100 20000 0 max. speed [rpm] resolution [steps / rev] speed rpm 0 20 40 60 80 100 ring diameter [mm] In off-axis rotary applications, very high angular resolutions are possible with the AS5311. The number of steps per revolution increases linearly with ring diameter. Due to the increasing number of pulses per revolution, the maximum speed decreases with increasing ring diameter. Example: A magnetic ring with 41.7mm diameter has a resolution of 65536 steps per revolution (16-bit) and a maximum speed of 305 rpm. Res [bit] Steps per Revolution Ring Diameter [mm] Maximum Speed [rpm] 15 32768 20.9 609 16 65536 41.7 305 17 131072 83.4 152 www.ams.com/AS5311 Revision 1.12 23 - 29 AS5311 Datasheet - A p p l i c a t i o n I n f o r m a t i o n The number of incremental steps per revolution can be calculated as: (EQ 3) incremental _ steps = 1024 * nbr _ polepairs (EQ 4) incremental _ steps = 1024 * d * π 2 Note: The circumference (d*π) must be a multiple of one polepair = 2mm, hence the diameter of the magnet ring may need to be adjusted accordingly: (EQ 5) d= nbr _ polepairs * 2mm π The maximum rotational speed can be calculated as: (EQ 6) max_ rot _ speed = max_ lin _ speed * 60 39000 = d *π d *π Where: nbr_polepairs is the number of pole pairs at the magnet ring. d is the diameter of the ring in mm; the diameter is taken at the locus of the Hall elements underneath the magnet. max_rot_speed is the maximum rotational speed in revolutions per minute rpm. max_lin_speed is the maximum linear speed in mm/sec (=650 mm/s for AS5311). Note: Further examples are shown in the “Magnet Selection Guide”, available for download from the ams website. www.ams.com/AS5311 Revision 1.12 24 - 29 AS5311 Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s 9 Package Drawings and Markings The device is available in a 20-pin TSSOP package. Figure 17. 20-pin TSSOP Package Dimensions and Hall Array Location Symbol A A1 A2 b c D E E1 e L L1 R R1 S θ1 θ2 θ3 aaa bbb ccc ddd N AS5311 YYWWMZZ @ Pin 1 identification Min 0.05 0.80 0.19 0.09 6.40 4.30 0.45 0.09 0.09 0.20 0° - Nom 1.00 6.50 6.40 BSC 4.40 Max 1.20 0.15 1.05 0.30 0.20 6.60 4.50 0.65 BSC 0.60 1.00 REF 12 REF 12 REF 0.10 0.10 0.05 0.20 20 0.75 8° - Notes: 1. Dimensions & Tolerancing confirm to ASME Y14.5M-1994. 2. All dimensions are in millimeters. Angles are in degrees. www.ams.com/AS5311 Revision 1.12 25 - 29 AS5311 Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s Marking: YYWWMZZ. YY WW M ZZ @ Year Manufacturing Week Plant Identifier Traceability Code Sublot Identifier Note: IC's marked with a white dot or the letters "ES" denote Engineering Samples. JEDEC Package Outline Standard: MO - 153 Thermal Resistance Rth(j-a): 89 K/W in still air, soldered on PCB 9.1 Recommended PCB Footprint Figure 18. PCB Footprint Recommended Footprint Data Symbol mm inch A 7.00 0.276 B 5.00 0.197 C 0.38 0.015 D 0.65 0.026 E 6.23 0.245 www.ams.com/AS5311 Revision 1.12 26 - 29 AS5311 Datasheet - R e v i s i o n H i s t o r y Revision History Revision Date Owner Description jja / jlu Recommended PCB Footprint (page 26) updated 1.1 26 Jun, 2009 1.2 09 Apr, 2010 1.3 24 Sep, 2010 1.6 08 Nov, 2011 Added few lines in Magnetic Input Specification (page 7) and edited the footnote in Data Contents (page 13) 1.7 01 Mar, 2012 Updated Figure 7 and Section 7.1.1 and Section 7.3 1.8 12 Mar, 2012 Updated Package Drawings and Markings, Absolute Maximum Ratings, Figure 14 and Ordering Information 1.9 11 Apr, 2012 1.10 13 Jun, 2012 Updated Section 7.5 and Table 1 1.11 21 Jun, 2012 Updated Table 2 1.12 12 Apr, 2013 Updated Figure 14 Ordering Information (page 28) updated agt rph Updated Figure 7 Updated Ordering Information, General Description and Pin Descriptions Note: Typos may not be explicitly mentioned under revision history. www.ams.com/AS5311 Revision 1.12 27 - 29 AS5311 Datasheet - O r d e r i n g I n f o r m a t i o n 10 Ordering Information The devices are available as the standard products shown in Table 14. Table 14. Ordering Information Ordering Code Description Delivery Form AS5311-ATSU 1 box = 100 tubes à 74 devices Tubes AS5311-ATST 1 reel = 1000 devices 1 reel = 4500 devices Tape & Reel Package 20-pin TSSOP Note: All products are RoHS compliant and ams green. Buy our products or get free samples online at www.ams.com/ICdirect Technical Support is available at www.ams.com/Technical-Support For further information and requests, email us at [email protected] (or) find your local distributor at www.ams.com/distributor www.ams.com/AS5311 Revision 1.12 28 - 29 AS5311 Datasheet - C o p y r i g h t s Copyrights Copyright © 1997-2013, ams AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. All products and companies mentioned are trademarks or registered trademarks of their respective companies. Disclaimer Devices sold by ams AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. ams AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. ams AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with ams AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by ams AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location. The information furnished here by ams AG is believed to be correct and accurate. However, ams AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of ams AG rendering of technical or other services. Contact Information Headquarters ams AG Tobelbaderstrasse 30 A-8141 Unterpremstaetten, Austria Tel Fax : +43 (0) 3136 500 0 : +43 (0) 3136 525 01 For Sales Offices, Distributors and Representatives, please visit: http://www.ams.com/contact www.ams.com/AS5311 Revision 1.12 29 - 29