ASR002-10E

Smart TMR Angle Sensor ASR002 Smart SPI TMR Angle Sensor Features Rotational speeds to 375,000 RPM 3.3 volt or 5 volt compatible four-wire SPI interface Robust airgap and misalignment tolerances Factory calibrated Ultraminiature 2.5 x 2.5 x 0.8 mm TDFN6 package • • • • • Key Specifications • 0.1° resolution • ±0.2° repeatability • Robust 6 to 20 mT (60 to 200 Oe) field operating range • Fast 12.5 kSps sample rate • Flexible 2.2 to 3.6 V supply range • Low 4 mA typical supply current • Full −40 °C to 125 °C operating range Applications • Rotary encoders • Robotics • Motor control • Automotive applications • Internet of Things (IoT) end nodes Block Diagram TMR Angle Sensor ADC Digital Signal Processing Description ASR002 TMR Smart Angle Sensors provide a precise digital angle measurement over a wide range of speeds. SPI Interface The sensor combines precise, low-power Tunneling Magnetoresistance (TMR) sensing elements with sophisticated digital signal processing. Transfer Function The sensor is factory calibrated, with coefficients stored in internal memory. A four-wire SPI interface provides angle data and allows setting device parameters. Angle 360° The ASR002 is designed for harsh industrial or automotive environments with ESD protection, and full −40 °C to 125 °C operating temperature range. 1 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Boundary Ratings Parameter Supply voltage Input and output voltages (MISO, MOSI, SS, SCLK) Input current Storage temperature ESD (Human Body Model) Applied magnetic field Min. −12 −0.5 −100 −55 Max. 4.2 VCC+2.5 up to 5.8 +100 150 2000 Unlimited Units Volts Volts mA °C Volts Tesla 2 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Operating Specifications (Tmin to Tmax; 2.2 < V < 3.6 V unless otherwise stated) DD Parameter Operating temperature Supply voltage Supply current Power-on Reset supply voltage Brown-out power supply voltage Start-up time Magnetics Symbol Tmin; Tmax VDD IDD VPOR VBOR TSTA Applied magnetic field strength H Accuracy and Repeatability Angular resolution Angular hysteresis δ ⎎ Min. −40 2.2 0.75 6 60 Typ. 4 1.4 1 15 12 120 Max. 125 3.6 6 1.36 20 200 Angular Degrees 12.5 DR tR tF tCL tCH tSE tSDD tSDZ tSDH tSDS tSH tSEZ mT Oe ±2 ±3 ±6 ε VBUS VIL VIH IOL CI/O Max. at VDD = 3.6V 0.1 ±0.2 Angular accuracy, variable bias2 Speed Sample rate SPI Bus Characteristics Bus voltage Low level input threshold voltage High level input threshold voltage Low level output current I/O capacitance SPI Setup and Hold Timing Data transfer rate SCLK Rise time SCLK fall time SCLK low time SCLK fall time SS to SCLK setup SCLK to MISO valid SS to MISO tri-state SCLK to MOSI hold time MOSI to SCLK setup SCLK to SS hold time SS to MISO valid RAM Timing Address setup time Data read time Nonvolatile Memory Characteristics Address setup time Data read time Data write time Endurance Package Thermal Characteristics Junction-to-ambient thermal resistance Package power dissipation Test Condition 0.1 Repeatability Angular accuracy, fixed bias1 Units °C V mA V V ms 2.2 0.8 kSps 5.5 10 V V V mA pF 2 Mbits/s Full duplex ns ns ns ns ns ns ns ns ns ns ns See figure 7 See figure 4 2.2 3 200 200 80 170 170 80 80 80 170 tADDR tREAD 3 10 µs µs tADDR tREAD tNVM 3 10 20 10000 µs µs ms Cycles 320 500 °C/W mW θJA Fixed temperature and bias1 0 to 85°C −40 to 125°C −40 to 125°C VOL = 0.4V See figure 5 3 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Specification Notes: 1. “Fixed Bias” means a fixed airgap within between the bias magnet and sensor so the magnitude of the magnetic field at the sensor is constant within the specified field range of the parts. The highest accuracy is obtained using fields closest to the 17.5 mT (175 Oe) factory calibration field. 2. “Variable Bias” means the magnitude of the magnetic field at the sensor can vary across the entire specification range. 4 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor ASR002 Overview The ASR002 is a non-contact angle sensor designed for high speed applications where size is limited. The heart of the ASR002 is a tunneling magnetoresistive (TMR) sensor. In a typical configuration, an external magnet provides a magnetic field of 6 to 20 mT (60 to 200 Oe) in the plane of the sensor, as illustrated below for a bar magnet and a diametrically-magnetized disk magnet. Factory-programmed signal conditioning is combined with a temperature sensor and digital linearization to produce high speed, accuracy, and precision in a tiny 2.5 x 2.5 mm TDFN package. Figure 1. Sensor operation. ASR002 Operation A detailed block diagram is shown below: Digital Core Nonvolatile Memory SPI Controller Calibration 12-bit ADC TMR Angle Sensor Digital Filter Calibration Coefficients SPI Interface Figure 2. Detailed block diagram. TMR Angle Sensor Element ASR002 sensors use unique TMR sensor elements that are inherently high speed and low noise. The digital core calculates the angle from sensor element Sine and Cosine vectors, and the raw sensor data are available from separate memory locations. ADC The sensor output is digitized with a 12-bit ADC. The extra bits ensure precision and computational accuracy. Digital Filter A first-order Infinite Impulse Response (IIR) digital filter with a programmable cutoff frequency can be used for ultralow noise if high-frequency operation is required. The factory default is the filter turned off. 5 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Rotation Direction The ASR002 can provide increasing angle values for either clockwise or counterclockwise field rotations. Counterclockwise is defined as a rotating field vector through pins 1-3-4-6, and clockwise through pins 1-6-4-3. The rotation direction can be programmed using the θDIR parameter. Figure 3. Zero-angle reference (θ0) and rotation direction (θDIR).The rotational center of the sensor is the package center. Zero-Angle Reference Point A programmable parameter θ0 sets the zero-degree reference or angular offset. This is the angle of “discontinuity,” that is, where the angle output changes from 360° to 0°. The default θ0 value is zero for magnetic fields pointing from pin 1 to pin 6. Direction and Hysteresis The Direction output indicates direction of rotation. A hysteresis setting can be changed to prevent small changes from causing the Direction output to “chatter,” especially at low speed. Digital Filter The digital filter is an Infinite impulse response (IIR) weighted running average filter, which can reduce mechanical and electrical noise depending on the required speed. The filtered output is calculated as follows: q q /m [(m-1)/m] q Where θ = is the measured angle; θn = the filtered angle; θn-1 is the previous value of the filtered angle; and m is a constant that determines the cutoff frequency as follows: fCUTOFF = fSAMPLE/(2π m) Where fCUTOFF is the filter cutoff frequency and fSAMPLE is the sensor ADC sampling rate (approximately 12500/s). So for example, if m = 10, the cutoff frequency is approximately 200 Hz. m = 1 disables filter so the output is simply updated with each sample. A Simple SPI Interface The SPI interface is an industry standard four-wire, full-duplex 2 megabit per second connection with the sensor as the slave to an external master such as a microcontroller. SPI data (MOSI and MISO) and the Clock (SCLK) are 2.2 volt to five-volt compliant. The digital angle is the default two byte response. The ASR002 uses an industry-standard “Mode 0” interface (data is sampled at the leading rising edge of the clock; CPOL=0 and CPHA=0). In accordance with industry standards, slave select (SS) is active-low, and bit order and byte order are from MSB to LSB. Details are shown in the following timing diagrams: 6 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor SCLK MOSI Address MISO SS tADDR tREAD Figure 4a. Sending the address for a read. SCLK MOSI D2 (LSB) D1 (MSB) MISO SS tADDR tREAD Figure 4b. Reading data. SCLK "1" indicates write Address MOSI MISO SS tREAD tADDR Figure 5a. Sending the address for a write. SCLK MOSI D2 (LSB) D1 (MSB) MISO SS tADDR t NVM Figure 5b. Writing data. MOSI Address Address Address tREAD tREAD MSB MISO LSB MSB LSB Figure 6. Continuous read. 7 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor SPI setup and hold timing constraints are shown in Figure 7: SS tF tCL tSE SCLK tCH tR tSH tSDH tSDS MOSI tSEZ tSDZ tSDD MISO Figure 7. SPI setup and hold timing. A schematic of a typical interface to a 3.3-volt or five-volt microcontroller is show in Figure 10. Straightforward Reading and Writing The sensor is reset on a falling edge of SS. All reads and writes are initiated by the master pulling SS “LOW” and sending an eight-bit address to the ASR002 plus a second byte. The least significant bit of the second address byte indicates whether the address request is for a read or a write (“0” is a read; “1” is a write). The slave responds with two bytes of data. As shown in figures 4 and 5, and the specification table, a 3 µs delay (tADDR) is needed between address bytes; 10 µs (tREAD) should be allowed before data can be read, and 20 ms (tNVM) should be allowed for writing parameters to the nonvolatile memory. Reading the angle To read the angle, the master simply writes two zero bytes for the “0” angle address, then reads the two-byte angle, which is expressed in tenths of degrees. These two-byte reads can be repeated to continuously read the angle as shown in the Figure 6 timing diagram and the code on p. 14. Reading and writing parameters Reading and writing parameters are simple four-byte sequences. The master writes two bytes for the parameter address, then reads or writes two bytes for the parameter value. Illustrative code to zero the sensor by writing the offset parameter is shown on p. 15. The number of bits in different parameters varies. Unused bits are sent as zeros by the sensor. Similarly, unused bits should be written as zeros to the sensor to avoid an out-of-range parameter that could be ignored. Because of the slower speed of the sensor’s nonvolatile memory, allow 15 ms for parameter writes. 8 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Memory Map The ASR002 memory provides access to angle data and user-programmable parameters. The memory is accessed via SPI as described in the SPI interface section. Parameter Symbol Angle Raw Sin Vector θ Sinθ Raw Cos Vector Cosθ Direction Default Read/ Write Range Data 0 – 3600 N/A R Address Description 0x00 0x01 In tenths of a degree Raw outputs centered at approx. 2048 with peak-peak amplitudes of approx. 1000. 0 = decreasing angle 1 = increasing angle Approx. 1500 – 2500 0x02 0–1 0x03 Dir User-Programmable Parameters Rotation Direction Angular Offset θDIR 0 0–1 0x40 [bit 0] θ0 0 0 – 3600 0x41 [bits 13:0] R/W Digital Filter Constant Direction Hysteresis m 1 1 – 255 0x42 δDIR 25 0 – 255 (0 – 25.5°) 0x43 0  increasing CCW; 1  increasing CW (see Fig. 3) Point at which angle is zero (see Fig. 3) fCUTOFF= fSAMPLE/(2π m); fSAMPLE = approx. 12.5 kSps m = 1 disables filter Hysteresis of the “Dir” output; in tenths of a degree Read-Only Memory YY Lot code WW 0x80 N/A R N/A (ASCII) XX 0x81 0x82 ASCII date code in the form YYWWXX, where: YY = year; WW = work week; XX = internal code. Table 1. ASR002 Memory Locations. 9 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Power-Up and Initialization Absolute position Unlike some encoder types, ASR002 sensors detect absolute position and maintain position information when the power is removed. The sensor powers up indicating the correct position. Nonvolatile parameters All parameters are nonvolatile so they can be set once (via SPI), and remain for the life of the product if desired. Minimizing Noise Several steps minimize noise: • A 10 µF bypass capacitor is recommended as close as possible to the VDD and GND pins. A 0.080 x 0.050 inch or smaller capacitor is recommended to minimize magnetic interference with the sensor. • Use a circuit board ground plane. • Grounding the sensor’s center pad allows the leadframe to act as a shield. 10 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Magnet Selection The sensor’s wide operating field range of 6 to 20 mT (60 to 200 Oe) allows inexpensive magnets and operation over a wide range of magnet spacing. The figures below show the magnetic field for various magnet geometries and distances for inexpensive C5/Y25 grade ferrite magnets: 240 t = 1 mm t=2 t=4 t=8 180 Magnetic Field (Oe) Magnetic Field (Oe) 240 Ferrite (C5/Y25) 120 d=8 60 M 0 0 d = 4 mm d=8 d = 12 d = 16 180 Ferrite (C5/Y25) 120 60 t d M 3 6 9 sensor-magnet separation (mm) 0 0 12 t=4 6 12 sensor-magnet separation (mm) 18 Figure 8. Magnetic fields for various geometries of C5/Y25 ferrite magnets plotted for the distance between the magnet and sensor. Eight-millimeter diameter magnets of various thicknesses are shown at left, and four-millimeter thick magnets of various diameters are shown at right. Field varies less with distance for larger magnets, so maximizing magnet size within the mechanical constraints of the system maximizes accuracy. Higher-grade magnets can be used for high-temperature applications or large magnet-sensor separations. The graph below shows field strengths with various materials: Magnetic Field (Oe) 240 AlNiCo-8 AlNiCo-5 SmCo (28) NdFeB (Nd45) Ferrite (C1/Y10) Ferrite (C5/Y25) 180 120 d=8 60 M 0 0 t=4 6 12 sensor-magnet separation (mm) 18 Figure 9. Magnetic fields from an 8 millimeter diameter, 4 millimeter thick magnet for increasing magnet-sensor separation. NdFeB materials produce the largest magnetic fields and separations. SmCo and AlNiCo materials offer the highest operating temperatures. Ferrite magnets are the most cost-effective. Our free Web app can be used to determine optimum separations for various magnet sizes and materials: https://www.nve.com/spec/calculators.php. NVE’s Online Store stocks popular magnets. 11 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Application Circuits Typical Microcontrollers Interface A typical microcontroller interface is shown below: 2.2 - 3.6 V ASR002-10E 3.3 - 5 V VDD VDD Microcontroller 10 µF SS SS SCLK SCLK MISO MISO MOSI MOSI GND GND Figure 10. Typical microcontroller interface. The ASR002 is configured as a Slave and the microcontroller should be configured as the Master. The ASR002 SPI interface is compatible with 3.3 or five-volt microcontrollers. 12 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation sensor-apps@nve.com Smart TMR Angle Sensor Typical Read and Write Communications Pseudocode //SPI clock set elsewhere (2 MHz max.) //SPSR = SPI Status Register; SPIF = SPI Status Register Interrupt flag //SS set low (active) elsewhere { case COMM_GET_MEM: //Routine to READ memory SPDR=buffer[1]; //Sends the address to read from while(! (SPSR & (1