MA820GQ-Z

MagAlpha MA820 8-Bit Contactless Angle Encoder with ABZ Output and Push Button Function DESCRIPTION FEATURES The MA820 is an easy-to-use, magnetic, angle encoder designed to replace analogic potentiometers or rotary switches. The MA820 is designed for slow operation such as humanmachine interface, manual controls, etc. where the rotating speed remains below 200 rpm. The sensor detects the absolute angular position of a permanent magnet attached to a rotating shaft and outputs incremental ABZ encoder data. The number of pulses per channel for each A or B output is programmable from 1 to 64 via an SPI interface.   Magnet shapes and configurations are very flexible. Typically, the MA820 is used with a diametrically magnetized cylinder of 2 - 8mm in diameter. The MA820 features programmable magnetic field strength thresholds, which allow for the implementation of a push or pull button function. These are output as two logic signals. On-chip non-volatile memory provides storage for configuration parameters, including the reference zero angle position, ABZ pulses per channel, and magnetic field detection threshold settings.       8-Bit Resolution Absolute Angle Encoder Contactless Sensing for Long Life with No Wear SPI Serial Interface for Chip Configuration Incremental ABZ Encoder Interface with 1 64 Programmable Pulses Per Channel Programmable Magnetic Field Strength Detection for Push/Pull Button Detection 3.3V, 12mA Supply -40 to +125°C Operating Temperature Available in a QFN-16 (3mmx3mm) Package APPLICATIONS      Rotary Knob Control Interfaces Manual Controls Encoders Automotive White Goods All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For MPS green status, please visit the MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 1 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ ORDERING INFORMATION Part Number* MA820GQ Package QFN-16 (3mmx3mm) Top Marking See Below * For Tape & Reel, add suffix –Z (e.g. MA820GQ–Z) TOP MARKING AXX: product code of MA820GQ Y: year code LLL: lot number PACKAGE REFERENCE TOP VIEW GND MISO 8 /Z 7 B CS 6 5 9 4 MOSI 3 Z TEST 10 MGL 11 2 A SCLK 12 1 /A 17 PAD 13 14 15 16 VDD N/C /B MGH QFN-16 (3mmx3mm) MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 2 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ ABSOLUTE MAXIMUM RATINGS (1) Supply voltage ............................ -0.5V to +4.6V Input pin voltage (VI) ................... -0.5V to +6.0V Output pin voltage (VO) ............... -0.5V to +4.6V (2) Continuous power dissipation (TA = +25°C) ..................................................................2.0W Junction temperature ............................... 125°C Lead temperature .................................... 260°C Storage temperature .................. -65°C to 150°C MA820 Rev. 1.01 6/15/2018 (3) Thermal Resistance θJA θJC QFN-16 (3mmx3mm) ............ 50 ....... 12 ... °C/W NOTES: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/θJA. 3) Measured on JESD51-7, 4-layer PCB. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 3 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ ELECTRICAL CHARACTERISTICS Parameter Symbol Condition Recommended Operating Conditions Min Typ Max Units Supply voltage VDD 3.0 3.3 3.6 V Supply current IDD 10.2 11.7 13.8 mA Operating temperature Top -40 Applied magnetic field B 30 MA820 Rev. 1.01 6/15/2018 125 60 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. °C mT 4 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ GENERAL CHARACTERISTICS VDD = 3.3V, 45mT < B < 100mT, Temp = -40°C to +125°C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units 20 4 90 ms ms Hz 0.7 deg 1.1 deg Response Time (4) Power-up time (5) Latency (4) Filter cutoff frequency Accuracy Constant speed propagation delay Fcutoff At room temperature over the full field range Over the full temperature range and field range INL at 25°C INL between -40°C to +125°C (5) Output Drift Temperature induced drift at (5) room temperature Temperature induced variation (5) 0.015 0.04 deg/°C From 25°C to 85°C 0.5 1.2 deg From 25°C to 125°C 1.0 0.005 2.1 deg deg/mT deg/V (5) Magnetic field induced (5) Voltage supply induced Incremental Output – ABZ 0.3 ABZ update rate Resolution - edges per turn Pulses per channel per turn (5) ABZ hysteresis (5) Systematic jitter Random jitter (3σ) Overall ABZ jitter Absolute Output – Serial 16 PPT+1 H Programmable 4 256 Programmable 1 64 2.1 6.0 0.6 0.4 deg % % deg 1100 kHz 8 bit For PPT = 63, 0 - 100krpm For PPT = 63, 0 - 100krpm Refresh rate 850 Data output length Magnetic Field Detection Thresholds VIH VIL RPU RPD Input low voltage Pull-up resistor Pull-down resistor Rising edge slew rate 5 6 -600 MagHys Input high voltage 980 8 (5) Accuracy (5) Hysteresis (5) Temperature drift Digital I/O MHz mT mT ppm/°C 2.5 5.5 V -0.3 0.8 V 46 66 97 kΩ 43 55 97 kΩ (4) TR CL = 50pF 0.7 V/ns (4) TF CL = 50pF 0.7 V/ns Falling edge slew rate NOTES: 4) Guaranteed by design. 5) Guaranteed by characteristic test. MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 5 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ TYPICAL CHARACTERISTICS VDD = 3.3V, Temp = 25°C, unless otherwise noted. ABZ Jitter at PPT = 63 Filter Transfer Function Error Curves at 50mT 2 1.1 5 1.5 1 0.8 0.7 0.6 0.5 1 0 -5 -45癈 0 -0.5 -10 -1 -15 0.4 25癈 125癈 0.5 -3 dB ERROR (deg) FILTER TRANSFER FUNCTION (dB) RANDOM JITTER (%) 0.9 -1.5 0.3 -2 0.1 1 10 100 1000 10 4 10 5 -20 0 1 10 100 1000 10 50 100 150 200 250 300 350 4 ROTATION SPEED (rpm) ANGLE (deg) f (Hz) Non-Linearity (INL and Harmonics) Current Consumption at VDD = 3.3V 1.5 12 11.5 SUPPLY CURRENT (mA) NON-LINEARITY (deg) INL 1 H1 0.5 H2 11 10.5 10 0 0 20 40 60 MAGNETIC FIELD (T) MA820 Rev. 1.01 6/15/2018 80 100 -50 0 50 100 150 TEMPERATURE (癈 ) www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 6 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ PIN FUNCTIONS Package Pin # Name Description 1 2 3 4 /A A Z MOSI Channel A inverted. A is the output of the incremental interface. Channel A. A is the output of the incremental interface. Index pulse Z. Z is the output of the incremental interface. Data in (SPI). MOSI has an internal pull-down resistor. 5 6 CS B 7 MISO 8 9 10 11 GND /Z TEST MGL Chip select (SPI). CS has an internal pull-up resistor. Channel B. B is the output of the incremental interface. Data out (SPI). MISO has an internal pull-down resistor that is enabled at a high impedance state. Supply ground. Index pulse Z inverted. Z is the output of the incremental interface. Connect to ground. Digital output indicating field strength below MGLT level. 12 13 14 15 16 SCLK VDD N/C /B MGH Clock (SPI). SCLK has an internal pull-down resistor. Supply 3.3V. No connection. Leave N/C unconnected. Channel B inverted. B is the output of the incremental interface. Digital output indicating field strength above MGHT level. MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 7 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ BLOCK DIAGRAM Figure 1: Functional Block Diagram MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 8 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ OPERATION Sensor Front-End The magnetic field is detected with integrated Hall devices located in the center of the package. The angle is measured using the SpinaxisTM method, which digitizes the direction of the field directly without complex arctangent computation or feedback loop-based circuits (interpolators). The SpinaxisTM method is based on phase detection and generates a sinusoidal signal with a phase that represents the angle of the magnetic field. The angle is then obtained by a time-to-digital converter, which measures the time between the zero crossing of the sinusoidal signal and the edge of a constant waveform (see Figure 2). The time-to-digital is output from the front-end to the digital conditioning block. Sensor – Magnet Mounting The sensitive volume of the MA820 is confined in a region less than 100µm wide and has multiple integrated Hall devices. This volume is located both horizontally and vertically within 50µm of the center of the QFN package. The sensor detects the angle of the magnetic field projected in a plane parallel to the package’s upper surface. This means that the only relevant magnetic field is the in-plane component (X and Y components) in the middle point of the package. By default, when looking at the top of the package, the angle increases when the magnetic field rotates clockwise. Figure 3 shows the zero angle of the unprogrammed sensor, where the cross indicates the sensitive point. Both the rotation direction and the zero angle can be programmed. Top: Sine Waveform Bottom: Clock of Time-to-Digital Converter Figure 2: Phase Detection Method The output of the front-end delivers a digital number proportional to the angle of the magnetic field at the rate of 1MHz in a straightforward and open-loop manner. Digital Filtering The front-end signal is further treated to achieve the final effective resolution. This treatment does not add any latency in steady conditions. The filter transfer function can be calculated with Equation (1): H ( s)  1  2s (1  s) 2 (1) Where τ is the filter time constant related to the cutoff frequency by: τ = 0.38/Fcutoff. See the General Characteristics table on page 5 for the value of Fcutoff. MA820 Rev. 1.01 6/15/2018 Figure 3: Detection Point and Default Positive Direction This type of detection provides flexibility for the design of an angular encoder. The sensor only requires the magnetic vector to lie essentially within the sensor plane with a field amplitude of at least 30mT. Note that the MA820 can work with fields smaller than 30mT, but the linearity and resolution performance may deviate from the specifications. The most straightforward mounting method is to place the MA820 sensor on the rotation axis of a permanent magnet (i.e.: a diametrically magnetized cylinder) (see Figure 4). The recommended magnet is a Neodymium alloy (N35) cylinder with dimensions Ø5x3mm inserted into an aluminum shaft with a 1.5mm air gap between the magnet and the sensor (surface of package). For good linearity, the sensor is positioned with a precision of 0.5mm. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 9 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ In general, the MagAlpha works well with or without the exposed pad connected to anything. For optimum conditions (electrically, thermally, and mechanically), it is recommended that the exposed pad be connected to ground. Figure 4: End-of-Shaft Mounting Figure 5 shows an example of sensor and magnet mounting in a contactless switch assembly. A Neodymium alloy magnet is inserted into an aluminum shaft. The air gap between the magnet and the sensor is 1.0mm. The sensor is positioned on the rotation axis with a precision of 0.5mm. Serial Interface The sensor supports the SPI serial interface for register programming. SPI is a four-wire, synchronous, serial communication interface. The MagAlpha supports SPI Mode 3 and Mode 0 (see Table 1 and Table 2). The SPI Mode (0 or 3) is detected automatically by the sensor and therefore does not require any action from the user. The maximum clock rate supported on SPI is 25MHz. There is no minimum clock rate. Note that real-life data rates depend on the PCB layout quality and signal trace length. See Figure 7 and Table 3 for SPI timing. All commands to the MagAlpha (whether for writing or reading a register content) must be transferred through the SPI MOSI pin and must be 16 bits long. See the SPI Communication section on page 12 for details. Table 1: SPI Specification Figure 5: Example of Potentiometer-Like Assembly Electrical Mounting and Power Supply Decoupling It is recommended to place a 1µF decoupling capacitor close to the sensor with a low impedance path to GND (see Figure 6). SCLK idle state Data capture Data transmission CS idle state Data order Table 2: SPI Standard 3.3 V MGL MGH MISO Mode 0 Mode 3 Low High On SCLK rising edge On SCLK falling edge High MSB first CPOL CPHA Data order (DORD) Mode 0 Mode 3 0 1 0 1 0 (MSB first) MOSI VDD SCLK 1 mF MA820 GND CS A B TEST Exposed pad Z Figure 5: Connection for Supply Decoupling MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 10 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ tcsL CS tsclk tsclkL tsclkH tcsH tMISO tMISO tidleAngle tidleReg tnvm SCLK tMISO MISO hi-Z MOSI MSB X LSB MSB hi-Z MSB X LSB MSB tMOSI Figure 6: SPI Timing Diagram tidleAngle tidleAngle tidleAngle tidleReg tidleReg tidleAngle tnvm tidleReg CS MISO Angle Angle Angle Angle Reg Value Angle Angle Reg Value Angle MOSI 0 0 0 Read Reg Cmd 0 0 Write Reg Cmd 0 0 Figure 7: Minimum Idle Time Table 3: SPI Timing Parameter (6) Description Min Max tidleAngle Idle time between two subsequent angle transmissions 150 ns tidleReg Idle time before and after a register readout 750 ns tnvm Idle time between a write command and a register readout (delay necessary for non-volatile memory update) 20 ms tcsL Time between CS falling edge and SCLK falling edge 80 ns tsclk SCLK period 40 ns tsclkL Low level of SCLK signal 20 ns tsclkH High level of SCLK signal 20 ns tcsH Time between SCLK rising edge and CS rising edge 25 ns tMISO SCLK setting edge to data output valid tMOSI Data input valid to SCLK reading edge 15 15 Unit ns ns NOTE: 6) All values are guaranteed by design. MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 11 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ SPI Communication The sensor supports three types of SPI operation:    Read angle Read configuration register Write configuration register Each operation has a specific frame structure described below. SPI Read Angle See Figure 8 for the diagram of a full SPI angle reading. See Figure 10 for a partial SPI angle reading. A full angle reading requires 16 clock pulses. The sensor MISO line returns: MSB LSB MISO Angle(15:0) MOSI 0 The MagAlpha family has sensors with different features and levels of resolution. See the data output length section in the General Characteristics table on page 5 for the number of useful bits delivered at the serial output. If the data length is smaller than 16, the rest of the bits sent are zeros. SPI Read Register A read register operation is constituted of two 16-bit frames. The first frame sends a read request, which contains the 3-bit read command (010) followed by the 5-bit register address. The second frame returns the 8-bit register value (MSB byte). The last eight bits of the frame must all be set to zero. The first 16-bit SPI frame (read request) is: MSB MISO MOSI LSB Angle(15:0) command reg. address 0 1 0 A4 A3 A2 A1 A0 0 0 0 0 0 0 0 0 The second 16-bit SPI frame (response) is: reg. value MISO V7 V6 V5 V4 V3 V2 V1 V0 0 0 0 0 0 0 0 0 MSB LSB MOSI 0 See Figure overview. for a complete transmission For example, to get the value of the magnetic level high and low flags (MGH and MGL), read register 27 (bit 6, bit 7) by sending the following first frame: MSB MISO MOSI LSB Angle(15:0) command 0 1 0 reg. address 1 1 0 1 1 0 0 0 0 0 0 0 0 In the second frame, the MagAlpha replies: Figure 8: Full 16-Bit SPI Angle Reading reg. value MISO MGH MGL X X X X X X 0 0 0 0 0 0 0 0 MSB MOSI LSB 0 See Figure for a complete example. Figure 9: Partial 8-Bit SPI Angle Reading MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 12 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ Figure 11: Two 16-Bit Frames Read Register Operation Figure 12: Example Read Magnetic Level Flags High and Low (MGH, MGH) on Register 27, Bit 7-6 SPI Write Register Table 4 shows the programmable 8-bit registers. Data written to these registers are stored in the on-chip non-volatile memory and reloaded during power-on automatically. The factory default register values are shown in Table 5. A write register operation is constituted of two 16-bit frames. The first frame sends a write request, which contains the 3-bit write command (100) followed by the 5-bit register address and the 8-bit value (MSB first). The second frame returns the newly written register value (acknowledge). request and read angle do not require this wait time. First 16-bit SPI frame (write request): MSB LSB MISO Angle(15:0) MOSI command reg. address reg. value 1 0 0 A4 A3 A2 A1 A0 V7 V6 V5 V4 V3 V2 V1 V0 Second 16-bit SPI frame (response): reg. value MISO V7 V6 V5 V4 V3 V2 V1 V0 0 0 0 0 0 0 0 0 MSB The on-chip memory is guaranteed to endure 1,000 write cycles at 25°C. It is critical to wait 20ms between the first and second frame. This is the time taken to write the non-volatile memory. Failure to implement this wait period results in the register’s previous value being read. Note that this delay is only required after a write request. A read register MA820 Rev. 1.01 6/15/2018 MOSI LSB 0 The read-back register content can be used to verify the register programming. Figure 13 complete transmission overview. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 13 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ For example, to set the value of the output rotation direction (RD) to counterclockwise (high), write register 9 by sending the following first frame: MSB MISO Send the second frame after a 20ms wait time. If the register is written correctly, the reply is: reg. value MISO 1 0 0 0 0 0 0 0 MSB Angle(15:0) MOSI MOSI command 1 0 0 0 0 0 0 0 0 0 0 LSB reg. address 0 1 0 0 1 reg. value 1 0 0 0 0 0 0 0 LSB 0 See Figure 14 for a complete example. Figure 13: Overview of Two 16-Bit Frames Write Register Operation Figure 14: Example Write Output Rotation Direction (RD) to Counterclockwise (High), on Register 9, Bit 7 MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 14 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ REGISTER MAP Table 4: Register Map Bit 7 MSB No Hex Bin 0 0x0 00000 Z(7:0) 1 0x1 00001 Z(15:8) 0x4 00100 5 0x5 00101 6 0x6 00110 9 0x9 01001 RD - - - - 27 0x1B 11011 MGH MGL - - - 4 (7) Bit 6 PPT(1:0) - - Bit 5 Bit 4 0 0 - - MGLT(2:0) Bit 3 Bit 2 Bit 1 Bit 0 LSB 0 0 0 0 PPT(5:2) MGHT(2:0) - - - - - - - - NOTE: 7) Bits (5:0) must be set to 000000. Table 5: Factory Default Values No Hex Bin Bit 7 MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 LSB 0 0x0 00000 0 0 0 0 0 0 0 0 1 0x1 00001 0 0 0 0 0 0 0 0 4 0x4 00100 1 1 0 0 0 0 0 0 5 0x5 00101 0 0 0 0 1 1 1 1 6 0x6 00110 0 0 0 1 1 1 0 0 9 0x9 01001 0 0 0 0 0 0 0 0 Table 6: Programming Parameters Parameters Symbol Number of Bits Description See Table Zero setting ABZ pulses per 360 deg turn Magnetic field high threshold Magnetic field low threshold Z 16 7 PPT 6 Set the zero position Sets the pulses per turn on each channel MGHT 3 Sets the field strength high threshold. 13 MGLT 3 Sets the field strength low threshold. 13 RD 1 Determines the sensor positive direction 9 Rotation direction MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 10 15 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ REGISTER SETTINGS Zero Setting The zero position of the MagAlpha (a0) can be programmed with 16 bits of resolution. The angle streamed out by the MagAlpha (aout) is given by Equation (2): aout  araw  a0 (2) Where araw is the raw angle provided by the MagAlpha front-end. The parameter Z(15:0), which is zero by default, is the complementary angle of the zero setting. In decimals, it can be written as shown in Equation (3): a0  2  Z (15 : 0) 16 Table 7: Zero Setting Parameter Zero pos. a0 (16 bit dec) 65536 65535 65534 … 2 1 0 1 2 … 65534 65535 Zero pos. a0 (deg) 360.000 359.995 359.989 … 0.011 0.005 Example To set the zero position to 20 deg, the Z(15:0) parameter must be equal to the complementary angle shown in Equation (4): Z (15 : 0)  216  20 deg 16 2  61895 360 deg RD Positive Direction 0 1 Clockwise (CW) Counterclockwise (CCW) ABZ Incremental Encoder Output The MA820 ABZ output emulates an 8-bit incremental encoder (such as an optical encoder) providing logic pulses in quadrature (see Figure 16). Compared to signal A, signal B is shifted by a quarter of the pulse period. Over one revolution, signal A pulses N times, where N is programmable from 1 to 64 pulses per revolution. The number of pulses per channel per revolution is programmed by setting the parameter PPT, which consists of six bits split between registers 0x4 and 0x5 (see Table 4). The factory default value is 64. Table 10 describes how to program PPT(5:0) to set the required resolution. Table 10: PPT (4) In binary, it is written as 1111 0001 1100 0111. Table 8 shows the content of registers 0 and 1. Table 8: Register Content Reg Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 0 1 1 0 0 0 1 1 1 1 1 1 1 1 0 0 0 1 Rotation Direction By default, when looking at the top of the package, the angle increases when the magnetic field rotates clockwise (CW) (see Figure 15 and Table 9). MA820 Rev. 1.01 6/15/2018 Table 9: Rotation Direction Parameter (3) Table 7 shows the zero setting parameter. Z(15:0) Figure 15: Positive Rotation Direction of the Magnetic Field PPT(5:0) 000000 000001 000010 000011 … 111100 111101 111110 111111 Pulses per Revolution 1 2 3 4 … 61 62 63 64 Edges per Revolution 4 8 12 16 … 244 248 252 256 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. MIN … MAX 16 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ For example, to set 30 pulses per revolution (120 edges), set PPT(5:0) to 30 - 1 = 29. In binary, this is written as 011101. The registers 0x4 and 0x5 must be set as shown in Table 11. Table 11: Register Setting for 30 Pulses Per Turn Reg Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 4 0 1 0 0 0 0 0 0 5 0 0 0 0 0 1 1 1 Figure 18: Hysteresis of the Incremental Output ABZ Jitter The ABZ state is updated at a frequency of 16MHz. The jitter characterizes how far a particular ABZ edge can occur at an angular position different from the ideal position (see Figure 19). Figure 16: Timing of the ABZ Output Signal Z (zero or index) raises only once per turn at the zero-angle position. The position and length of the Z pulse is programmable via bits ILIP(3:0) in register 0x5 (see Figure 17). Figure 19: ABZ Jitter The measurable jitter is composed by a systematic jitter (i.e.: always the same deviation at a given angle) and a random jitter. The random jitter reflects the sensor noise. Therefore, the edge distribution is the same as the SPI output noise. Like the sensor resolution, it is defined as the 3σ width of this distribution. Figure 17: ILIP Parameter Effect on Index Shape By default, the ILIP parameter is 0000. The index rising edge is aligned with the channel B falling edge. The index length is half the A or B pulse length. ABZ Hysteresis A hysteresis larger than the output noise is introduced on the ABZ output to avoid any spurious transitions (see Figure 18). MA820 Rev. 1.01 6/15/2018 In fact, the random jitter is a function of the rotation speed. At a lower speed, the random jitter is smaller than the sensor noise. This is a consequence of the fact that the probability of measuring an edge at a certain distance from the ideal position depends on the number of ABZ updates at this position. The minimum field for ABZ reading is 30mT. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 17 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ Magnetic Field Thresholds Push Button Detection The MA820 has two threshold options (MGHT or MGLT), which are complementary in operation. The flag MGH becomes true (logic 1) if the magnetic field increases above MGHT. The flag MGL becomes true (logic 1) if the magnetic field falls below MGLT (see Figure 20). In this way, it is possible to implement both a push or pull action. MagHys, the hysteresis on the signals MGH and MGL, is indicated in the General Characteristics table on page 5. The MGLT and MGHT thresholds are coded on three bits and stored in register 6 (see Table 12). Table 12: Register 6 Reg Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 6 MGLT MGHT The 3-bit values of MGLT and MGHT correspond to the magnetic field (see Table 13). Table 13: MGLT and MGHT Binary to mT Relation MGLT or (9) MGHT Figure 20: MGH and MGL Signals as a Function of the Field Strength The MGL/MGH flags can be used for detecting an approaching magnet (e.g.: when a button is pressed). With the 5mmx3mm magnet example, if the MGHT threshold is set to binary 110 (106 - 112mT), the MGH signal is set to logic high when the sensor-magnet airgap is smaller than 1.0mm (see Figure 21). 000 001 010 011 100 101 110 111 Field threshold in mT From low to high magnetic field 26 41 56 70 84 98 112 126 (8) From high to low magnetic field 20 35 50 64 78 92 106 120 NOTES: 8) Valid for VDD = 3.3V. If different, then the field threshold is scaled by the factor VDD/3.3V. 9) MGLT can have a larger value than MGHT. The alarm flags MGL and MGH can be read in register 27 (bit 6 and bit 7), and their logic state is also given at the digital output pins 11 and 16. To read the MGL and MGH flags by SPI, send the 8-bit command write to register 27: command 0 1 0 reg. address 1 1 0 1 1 value LSB 0 0 0 0 0 0 0 0 MSB The MA820 answers with the register 27 content in the next transmission: Reg Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 27 MGH MGL x x x x x x Figure 21: Magnetic Field Produced by a 5mmx3mm N35 Magnet as a Function of the Airgap with Threshold Set to 110mT MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 18 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ TYPICAL APPLICATION CIRCUIT Figure 22: Typical Connecton to a Host Microprocessor MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 19 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ PACKAGE INFORMATION QFN-16 (3mmx3mm) MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 20 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ APPENDIX A: DEFINITIONS Resolution (3σ noise level) This is the smallest angle increment distinguishable from the noise. The resolution is measured by computing three times σ (the standard deviation in degrees) taken over 1,000 data points at a constant position. The resolution in bits is obtained with log2(360/6σ). Refresh Rate Rate at which new data points are stored in the output buffer. ABZ Update Rate Rate at which a new ABZ sate is computed. The inverse of this rate is the minimum time between two ABZ edges. Latency The time elapsed between the instant when the data is ready to be read and the instant at which the shaft passes that position. The lag in degrees is lag  lantency  v , where v is the angular velocity in deg/s. Power-Up Time Time until the sensor delivers valid data starting at power up. Integral Non-Linearity (INL) Maximum deviation between the average sensor output (at a fixed position) and the true mechanical angle. Figure A1: Integral Non-linearity Drift MA820 Rev. 1.01 6/15/2018 Angle variation rate when one parameter is changed (e.g.: temperature, VDD) and all the others, including the shaft angle, are maintained constant. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 21 MA820 – 8-BIT, DIGITAL ANGLE SENSOR WITH ABZ APPENDIX B: SPI COMMUNICATION CHEATSHEET Read Angle Read Register Write Register NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MA820 Rev. 1.01 6/15/2018 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2018 MPS. All Rights Reserved. 22