MT6815 Magnetic Rotary Encoder IC

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1 Features and Benefits Based on advanced magnetic field sensing technology Non-contacting angle measurement and large air gap Up to 5krpm with propagation delay compensation Independent output interfaces: I 2 C, SPI, Analog, ABZ, PWM and UVW Incremental ABZ programmable binary and decimal pulse-counts: 2500, 2000, 000, 500, 200, 00, 2048, 024, 52, 256, 28, 64, 48, 32 pulses per cycle 4bit core resolution User programmable resolution & zero index position RoHS Compliant 20/65/EU SOP-8 or QFN-6 Package Applications Replacement of optical encoders Robotics control BLDC motor commutation Power tools. General Description The MagnTek rotary position sensor MT685 is based on advanced magnetic field sensing technology. The sensor contains two magnet field sensing element arrays. A rotating magnetic field in the x-y sensor plane delivers two sinusoidal output signals indicating the angle (α) between the sensor and the magnetic field direction. Within a homogeneous field in the X-Y plane, the output signals are relatively independent of the physical placement in the z direction. The sensor is only sensitive to the magnetic field direction as the sensing element output is specially designed to be independent from the magnet field strength. This allows the device to be less sensitive to magnet variations, stray magnetic fields, air gap changes and off-axis misalignment. The incremental ABZ output mode is available in this sensor series, making the chip suitable to replace various optical encoders. The maximum resolution is 2048 pulses /892 steps per revolution in binary mode and 2500 pulses /0,000 steps per revolution in decimal mode. Standard UVW output is provided for BLDC. The absolute angle position is also provided as PWM output or an analog signal proportional to VDD from a 2bit DAC. A standard I 2 C and SPI (3-wire or 4-wire) interface allows a host microcontroller to read 4-bit absolute angle position data from MT / 28

2 . General Description Pin Configuration SOP-8 Package QFN-6 Package Functional Diagram Absolute Maximum Ratings (Non-Operating) Electrical Characteristics Magnetic Input Specification Output Mode I/O Pin Configuration Step, Direction and Index output signal (SDI Mode) Quadrature A, B and Zero-position output signal (ABZ Mode) UVW Output Mode Analog Output Mode Pulse Width Modulation (PWM) Output Mode I 2 C Interface I 2 C Timing Diagram I 2 C Read Angle Registers I 2 C Burst Read I 2 C Write SPI Interface SPI Timing Diagram Wire SPI Wire SPI SPI Read Angle Registers Magnet Placement Mechanical Angle Direction Package Designator / 28

3 2. Pin Configuration 2.. SOP-8 Package Sensing Center Geometry Center.86±0.5 mm ±0.5 mm Figure : Pin Configuration for SOP-8 Package Pin Name # Type Description CSN Digital Input I 2 C/SPI Selection HVPP 2 Analog Input OTP Programming Supply or SPI/I 2 C Selection OUT 3 Analog/Digital Output Analog or PWM Output VDD 4 Power Supply 3.3~5.0V Supply A/U 5 Digital Input/Output Incremental Signal A/U or Speed or SPI MOSI or I 2 C Data B/V 6 Digital Input/Output Incremental Signal B/V or Direction or SPI MISO Z/W 7 Digital Input/Output Incremental Signal Z/W or Index or SPI clock or I 2 C Clock GND 8 Ground Ground Family Members Part number MT685CT Description SOP-8 package, tube pack (00pcs/tube) or tape & reel pack (3000pcs/reel) *SOP-8 Reflow Sensitivity Classification: MSL 3 3/ 28

4 2.2. QFN-6 Package Top View Bottom View Geometry Center ±0.5 mm Sensing Center ±0.5 mm ±0.5 mm.84±0.5 mm Figure 2: Pin Configuration for QFN-6 Package Pin Name # Type Description A Digital Input/Output Incremental Signal A or Speed or SPI MOSI or I 2 C Data B 2 Digital Input/Output Incremental Signal B or Direction or SPI MISO Z 3 Digital Input/Output Incremental Signal Z or Index or SPI clock or I 2 C Clock GND 4 Ground Ground CSN 5 Digital Input SPI/I 2 C Selection NC 6 NC NC 7 NC NC 8 NC NC 9 NC NC 0 NC OUT Analog/Digital Output Analog or PWM Output HVPP 2 Analog Input OTP Programming Supply or SPI/I 2 C Selection W 3 Digital Output W or Z V 4 Digital Output V or B or Direction Selection U 5 Digital Output U or -A VDD 6 Supply 3.3~5.0V Supply Family Members Part number MT685QT Description QFN-6 package, tape and reel pack (3000pcs/reel) *QFN-6 Reflow Sensitivity Classification: MSL 3 4/ 28

5 3. Functional Diagram The MT685 is manufactured in a CMOS standard process and uses advanced magnet sensing technology to sense the magnetic field distribution across the surface of the chip. The integrated magnetic sensing element array is placed around the center of the device and delivers a voltage representation of the magnetic field at the surface of the IC. VDD HVPP/MODE LDO NVM DSP DAC Magnetic Sensing Element G G OSC ADC ADC Cordic Calibration Interpolator PWM ABZ /-A-B-Z UVW SDI UVW SPI /I 2 C M U X OUT A B Z U V W GND Csn Figure 3: Simplified System Block Diagram Figure 3 shows a simplified block diagram of the chip, consisting of the magnetic sensing element modeled by two interleaved Wheatstone bridges to generate cosine and sine signals, gain stages, analog-to-digital converters (ADC) for signal conditioning, and a digital signal processing (DSP) unit for encoding. Other supporting blocks such as LDO, etc. are also included. 4. Absolute Maximum Ratings (Non-Operating) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only. Functional operation of the device at these or any other conditions beyond those indicated under Operating Conditions is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Parameter Notes Min. Max. Unit. DC voltage at pin VDD V DC voltage at pin HVPP V Storage temperature C Operating Temperature C Electrostatic discharge (HBM) ± 3 kv Electrostatic discharge (CDM) ±.5 kv 5/ 28

6 5. Electrical Characteristics Operating conditions: Ta= -40 to +50 C, VDD= V unless otherwise noted. Symbol Parameter Conditions Min. Typ. Max. Unit VDD Supply Voltage ~ V HVPP Supply Voltage V Idd Supply Current ma LSB Resolution (ABZ or SDI mode) N steps per Cycle (See Page, Resolution Table) 360 N Degrees INL Integral Non-Linearity, Fig.4 Note () - ± ±.5 Degrees DNL TN Hyst Differential Non-Linearity (ABZ or SDI mode), Fig.4 Transition Noise (ABZ or SDI mode) Hysteresis (ABZ mode) <=0 bit - - ±0. LSB > 0bit - - ±0.03 Degrees Deg-rms <=2 bit LSB >2 bit Degree T PwrUp Power-up Time VDD Ramp<0us ms T delay Propagation Delay Without Delay Compensation With Delay Compensation μs μs Analog Output Characteristics R OUT Analog Output Resistance Ω R L Pull-Up or Pull-Down - K - - Ω C L Loading Capacitor nf V Sat_High Saturation High Voltage I Load =ma %VDD V Sat_Low Saturation Low Voltage I Load =ma 2 5 %VDD DAC_LSB DAC LSB 2-bit DAC %VDD DAC_INL DAC Integral Non-Linearity ±3 LSB DAC_DNL DAC Differential Non-Linearity ±.5 LSB Ta=25 C, RMS V Noise Analog Output Noise value, excluding DAC quantization 0.02 %VDD noise Erm Ratiometric Error Note(2) % PWM Output Characteristics FPWM PWM Frequency Programmable Hz T Rise Rising Time C Load =nf us T Fall Falling Time C Load =nf us 6/ 28

7 Digital I/O Characteristics (Push-Pull Type in Normal Mode) V IH High level input voltage - 0.7*VDD - - V V IL Low level input voltage *VDD V V OH High level output voltage I OH =2mA VDD-0. - V V OL Low level output voltage I OL =2mA V I LK Input Leakage Current ± μa Timing Specifications t iov Incremental Output Valid Time μs Note (): The typical error value can be achieved at room temperature and with no off-axis misalignment error. The max error value can be achieved over operation temperature range, at maximum air gap and with worst-case off-axis misalignment error. Note (2): The analog output is by design ratiometric, i.e. it is proportional to the supply voltage VDD. The ratiometric error is calculated as follows. Erm Vout V V Vout 5V 00% 5V 023 0bit code 2 0 TN DNL+LSB INL 0.35 Actual curve Ideal curve degrees Figure 4: Drawing illustrating INL, DNL and TN (for 0-bit case) 7/ 28

8 6. Magnetic Input Specification Operating conditions: Ta= -40 to +25 C, VDD= V unless otherwise noted. Two-pole cylindrical diametrically magnetized source. Symbol Parameter Notes Min Typ Max Unit Dmag Diameter Recommended magnet: Ø8mm x 2.5mm for cylindrical magnets 8 - mm Tmag Thickness mm Bpk AG Magnetic input field amplitude Air Gap Measured at the IC surface Gauss Magnet to IC surface distance ( Figure 5) mm RS Rotation Speed KRPM DISP Off Axis Misalignment Misalignment error between sensor center and magnet axis ( Figure 5 ) mm TCmag TCmag2 Recommended magnet material and temperature drift NdFeB (Neodymium Iron Boron) SmCo (Samarium Cobalt) %/ C Figure 5: Magnet Arrangement 8/ 28

9 7. Output Mode The MT685 provides ABZ, SDI, UVW, PWM and Analog output modes. Also angle data could be transferred by I 2 C or SPI interface. 7.. I/O Pin Configuration For SOP-8 Package, ABZ (single end), SDI (single end), I 2 C and SPI are configured to Pin.5, Pin.6, and Pin.7. Analog or PWM output is configured to Pin.3. SOP-8 Package I/O Pin configuration: Mode I 2 3 Wire 4 Wire ABZ SDI ABZ SDI C UVW Pin # SPI SPI Single Single Differential Differential 5 SDA SDAT MOSI A S U N/A N/A 6 MISO B D V N/A N/A 7 SCL SCK SCK Z I W N/A N/A For QFN-6 Package, ABZ (single end or differential), SDI (single end or differential), UVW, I 2 C and SPI are configured to Pin., Pin.2, Pin.3, Pin.3, Pin.4 and Pin.5. Analog or PWM output is configured to Pin.. QFN-6 Package I/O Pin configuration: Mode 3 Wire 4 Wire ABZ SDI ABZ SDI I2C UVW Pin # SPI SPI Single Single Differential Differential SDA SDAT MOSI A S A S 2 MISO B D B D 3 SCL SCK SCK Z I Z I 3 W -Z -I 4 V -B -D 5 U -A -S Output Mode Register (OTP) Reg. Output_Mode<:0> Output Mode 00 ABZ Mode 0 SDI Mode 0 UVW Mode NA 9/ 28

10 VDD U/-A V/-B W/-Z 0.uf A/S Z/I/W B/D B/D/V Z/I 3 0 VDD 0.uf 4 5 A/S/U Figure 6: ABZ, SDI, UVW Output Reference Circuit 7.2. Step, Direction and Index output signal (SDI Mode) In this mode, output Step has a pulse width of LSB, output Dir indicates the direction of the magnet rotation; Output Index is the same as output Z in Quadrature A/B mode as shown in Figure Quadrature A, B and Zero-position output signal (ABZ Mode) As shown in Figure 7, when the magnet rotates clock-wise (CW), output A leads output B by /4 cycle (or LSB); When the magnet rotates counter-clock-wise (CCW), output B leads output A by /4 cycle. Output Z indicates the zero position of the magnet and the pulse width of Z is selectable as, 2 or 4 LSBs. It is guaranteed that one Z pulse is generated for every rotation. The zero position is user programmable A CW Mechanical Zero Position Rotation Direction Change Mechanical Zero Position CCW Hyst=0.5LSB B Z/Index LSB 2LSB 4LSB 2LSB 4LSB Step Dir CW CCW Figure 7: Typical Output Waveform for A/B/Z and Step/Dir/Index mode 0/ 28

11 The mechanical zero position could be programmed, it is a 2 bits data for 0~360. Z/Index Pulse Width Register (OTP) Reg. Z_Pulse_Width<:0> Width (LSBs) Zero Position Register (MTP) Reg. bit7 bit6 bit5 bit4 bit3 bit2 bit bit0 Zero_LSB Zero<7:0> Zero_MSB NA NA NA NA Zero<:8> ABZ Resolution Register (OTP) Reg. ABZ_Res<2:0> Reg. ABZ_INT Steps Per Cycle Pulses Per Cycle / / / 28

12 7.4. UVW Output Mode The MT685 provides U, V and W pulses which are 20 degrees (electrical) out of phase as shown in Figure 8. The cycles of UVW per rotation can be programmed. U U V V W W Clockwise Counter Clockwise Figure 8: Typical Output Waveform for U/V/W mode UVW Pole Pairs Register (OTP) Reg. UVW_Pairs<3:0> UVW Pole Pairs UVW_Pairs<3:0> UVW Pole Pairs / 28

13 7.5. Analog Output Mode The MT685 provide a rail-to-rail linear analog output by a build-in 2 bit DAC as shown in Figure 9. It s a linear transfer function of absolute angle and output voltage. To enable analog output, register Enable_Analog should be programmed to high. VDD 00% (Zero) Figure 9: Default Analog Output Analog or PWM Output Control Register (OTP) Reg. Enable Analog Pin.3(SOP-8), Pin.(QFN-6) 0 PWM Analog The reference circuit for analog output is shown in Figure 0, an external decoupling capacitor C (typical 0nf, maximum 00nf) is suggested for better performance. VDD U/-A V/-B W/-Z 0.uf Analog C Z/I/W B/D/V A/S B/D Z/I C Analog VDD 0.uf 4 5 A/S/U Figure 0: Analog Output Reference Circuit 3/ 28

14 The angle and voltage value of start-point, stop-point, Clamp_Low and Clamp_High could be programmed, also a Zero point could be programmed as shown in Figure. VDD Zero Clamp_High V_Stop V_Start Clamp_Low 0 A_Start A_Stop Zero 360 A_Start Degrees Analog Output Zero Point Figure : Analog Output Transfer function and Zero Point Analog Output Registers (MTP) Reg. Bit<7:4> Bit<3:0> Clamp_Low_LSB Clamp_Low<7:0> Clamp_High_LSB Clamp_High<7:0> Clamp_Msb Clamp_High<:8> Clamp_Low<:8> Zero_Lsb Zero<7:0> Zero_Msb NA Zero<:8> Start_Anlge_Lsb A_Start<7:0> Start_Angle_Msb NA A_Start<:8> Stop_Angle_Lsb A_Stop<7:0> Stop_Angle_Msb NA A_Stop<:8> Start_Voltage_Lsb V_Start<7:0> Stop_Voltage_Lsb V_Stop<7:0> Voltage_Msb V_Stop<:8> V_Start<:8> 4/ 28

15 7.6. Pulse Width Modulation (PWM) Output Mode The MT685 provides a digital Pulse Width Modulation (PWM) output, whose duty cycle is proportional to the measured angle as shown in Figure 3. PWM is a default output of Pin.3 (SOP-8) and Pin. (QFN-6). VDD U/-A V/-B W/-Z 0.uf A/S 2 PWM Z/I/W B/D/V B/D Z/I PWM VDD 0.uf 4 5 A/S/U Figure 2: PWM Output Reference Circuit PWM Resolution Register (OTP) Reg. PWM_Res<:0> Resolution PWM Frequency 00 0 bit 2.5 KHz 0 9 bit 5 KHz 0 bit.25 KHz 2 bit 625 Hz Angle Min. 0 Angle Max. 359.xx 2 N clock period (N=9,0,,2) 2 N + clock period (N=9,0,,2) /f PWM Figure 3: PWM Output 5/ 28

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17 I 2 C Read Angle Registers The slave ID of MT685 is b in 7 bit binary form. The 4 bits angle data is stored in internal register 0x03 and 0x04. Please follow the I 2 C timing of Figure 6 to read the angle data from 0x03 and 0x04. Note: Please read register 0x03 first and then read 0x04 Figure 6: I 2 C Single Byte Read Angle Data Register: Reg. Addr. bit7 bit6 bit5 bit4 bit3 bit2 bit bit0 0X03 Angle<3:6> 0X04 Angle<5:0> N/A N/A 0~360 absolute angle θ could be calculated by the below formula: 3 Angle i i 0 = / 28

18 I 2 C Burst Read The MT685 provides an I 2 C burst read mode as shown in Figure 7 for faster data rate than single byte read mode. Figure 7: I 2 C Burst Read I 2 C Write Figure 8: I 2 C Write 8/ 28

19 7.8. SPI Interface The MT685 also provides a 4-Wire or 3-Wire SPI (Register 3W_SPI should be programmed t to High to enable 3-Wire SPI Mode) interface for host MCU to read back digital absolute angle information from its internal registers. The reference circuit for SPI interface is shown in Figure 9 and Figure 20. VDD 0.uf MOSI MOSI MCU MISO SCK MCU MISO SCK CSN CSN VDD 0.uf Figure 9: 4-Wire SPI Reference Circuit VDD 0.uf SDAT SDAT MCU SCK MCU SCK CSN CSN VDD 0.uf Figure 20: 3-Wire SPI Reference Circuit 3-Wire SPI Enable Register (OTP) Reg. 3W_SPI SPI Interface 0 4 Wire 3 Wire 9/ 28

20 7.8.. SPI Timing Diagram The MT685 SPI uses mode=3 (CPOL=, CPHA=) to exchange data. As shown in figure 2, a data transfer starts with the falling edge of CSN. The MT685 samples data on the rising edge of SCK, and the data transfer finally stops with the rising edge of CSN. CSN TL TSCK TSCKL TSCKH TH SCK TSET MISO Data N Data N+ THOLD MOSI Data N Data N+ Figure 2: SPI Timing Diagram Symbol Notes Min Max. Unit TL Time between CSN falling edge and SCK falling edge 250 ns TSCK Clock period 400 () ns TSCKL Low period of clock 200 (2) ns TSCKH High period of clock 200 (2) ns TSET Setup time for MISO/MOSI data 50 ns THOLD Hold time for MISO/MOSI data 50 ns TH Time between SCK last rising edge and CSN rising edge 0.5 TSCK ns Notes: () The MT685 has a burst mode. When this mode is enabled, the chip internal clock frequency is doubled and the minimum TSCK also could be reduced to 200ns (2) The MT685 has a burst mode. When this mode is enabled, the chip internal clock frequency is doubled and the minimum TSCKL and TSCKH also could be reduced to 00ns 20/ 28

21 Wire SPI CSN SCK MOSI R/W A6 A5 A4 A3 A2 A A0 DI7 DI6 DI5 DI4 DI3 DI2 DI DI0 MISO DO7 DO6 DO5 DO4 DO3 DO2 DO DO0 Figure 22: 4-Wire SPI Timing An SPI data transfer starts with the falling edge of CSN and stops at the rising edge of CSN. SCK is the Serial Port Clock and it is controlled by the SPI master, it is high when there is no SPI transmission. MOSI (master input slave output) and MOSI (mast input slave output) is the Serial Port Data Input and Output, it is driven at the falling edge of CLK and should be captured at the rising edge of CLK. Bit 0: R/W bit, when it is 0, the data D7~D0 is written into the device,when it is, the data D7~D0 from the device is read. In latter case, the chip will drive data at the start of bit 8. Bit -7: Address A6~A0. This is the address field of the indexed register. Bit 8-5: Data DI7~DI0 (write mode). This is the data that will be written into the device (MSB first). Bit 8-5: Data DO7~DO0 (read mode). This is the data that will be read from the device (MSB first) Wire SPI CSN SCK SDAT R/W A6 A5 A4 A3 A2 A A0 D7 D6 D5 D4 D3 D2 D D0 Figure 23: 3-Wire SPI Timing An SPI data transfer starts with the falling edge of CSN and stops at the rising edge of CSN. SCK is the Serial Port Clock and it is controlled by the SPI master, it is high when there is no SPI transmission. SDAT is the Serial Port Data Input and Output, and it is driven at the falling edge of CLK and should be captured at the rising edge of SCK. Bit 0: RW bit. When 0, the data D7~D0 is written into the device. When, the data D7~D0 from the device is read. In latter case, the chip will drive data at the start of bit 8. Bit -7: address A6~A0. This is the address field of the indexed register. Bit 8-5: data D7~D0 (write mode). This is the data that will be written into the device (MSB first). Bit 8-5: data D7~D0 (read mode). This is the data that will be read from the device (MSB first). 2/ 28

22 SPI Read Angle Registers (e.g. 4-Wire SPI) CSN SCK MOSI Read Reg. 0x03 Read Reg. 0x04 MISO Data Reg. 0x03 Data Reg. 0x04 Figure 24: 4-Wire SPI Single Byte Read Angle Registers Angle Data Register Reg. Addr. bit7 bit6 bit5 bit4 bit3 bit2 bit bit0 0X03 Angle<3:6> 0X04 Angle<5:0> N/A N/A The 0~360 absolute angle θ could be calculated by the below formula: 3 Angle i i 0 = 360 The MT685 provides an SPI burst read mode for faster data rate than single byte read mode as shown in Figure 25. CSN SCK MOSI Read Reg. 0x03 MISO Data Reg. 0x03 Data Reg. 0x04 Data Reg. 0x03 Data Reg. 0x / 28 Data N Data N+ Figure 25: 4-Wire SPI Burst Read Angle Registers

23 CSN SCK SDAT Read Reg. 0x03 Data Reg. 0x03 Read Reg. 0x04 Data Reg. 0x04 MCU Output MT685 Output MCU Output MT685 Output Figure 26: 3-Wire SPI Single Byte Read Angle Registers CSN SCK SDAT Read Reg. 0x03 Data Reg. 0x03 Data Reg. 0x04 Data Reg. 0x03 Data Reg. 0x04 Data N Data N+ Figure 27: 3-Wire SPI Burst Read Angle Registers 23/ 28

24 8. Magnet Placement The MT685 is suitable for on-axis applications of angle measurement. The magnet should be mounted in a suitable environment where its magnetic field will not be distorted as shown in Figure 28. Rotation Axis MT685 MT685 Rotation Axis Rotation Axis MT685 MT685 Figure 28: Magnet Mounted Reference 24/ 28

25 Also it is required that the magnet s center axis be aligned with the sensing element center of MT685 with the air-gap as small as possible. Any misalignment introduces additional angle error and big air-gap also weakens the magnet field which could be sensed by the device. Magnets with larger radius are more tolerant to DISP (off-axis misalignment) and big AG (air-gap between Magnet and device). INL vs. DISP for Φ8 magnet INL(deg) DISP (mm) AG=mm AG=3mm AG=5mm INL(deg) INL vs. DISP for Φ0 magnet DISP (mm) AG=mm AG=3mm AG=5mm 2 INL vs. DISP for Φ6 magnet.5 INL(deg) 0.5 AG=mm AG=3mm AG=5mm DISP (mm) 25/ 28

26 9. Mechanical Angle Direction 0 degree 90 degree N S N S degree 270 degree N S 0 degree 90 degree N S N S N S degree 270 degree N S S N 26/ 28

27 0. Package Designator SOP-8 Z SENSING CENTER Y X Symbol Dimensions in Millimeters Dimensions in Inches Min Max Min Max A A A b c D E E e.270(bsc) 0.050(BSC) L θ X Y Z / 28

28 QFN-6 Y SENSING CENTER X Z Symbol Dimensions in Millimeters Dimensions in Inches Min Max Min Max A A A REF 0.008REF D E D E k 0.275REF 0.0REF b e 0.500REF 0.020REF L X Y Z / 28