MT6501 Magnetic Angle Sensor IC

Transcription

1 Features and Benefits Based on advanced magnetic field sensing technology Contactless angle measurement On Chip Signal Processing for Robust Absolute Position Sensing Programmable Measurement Range Programmable Linear Transfer Characteristic Selectable Analog(Ratio metric), PWM or Switch(SO) Output 12bit Resolution Single chip solution RoHS Compliant 2011/6/EU 3-Wire SPI Interface Applications Contactless potentiometer Steering Angle Sensor for EPS Servo Motor Control 1. General Description The MagnTek rotary position sensor MT601 is an IC based on advanced magnetic field sensing technology. The sensor contains two Wheatstone bridges formed by a magnet field sensing element array. 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 (air gap). 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. This contactless system measures the absolute angle of a diametrically magnetized on-axis magnet. It is especially suitable for applications such as contactless potentiometer, EPS steering angle sensor, etc. 1/ 1

2 2. Pin Configuration X Y Figure 1: Pin Configuration for SOP-8 Package Also showing sensor element center location (mm) and angle rotation direction Name Number Type Description 1 Supply V supply CSN/T0 2 Digital I/O Chip select for SPI or Test0 SWO/T1 3 Digital I/O Switch Output or Test1 SCLK 4 Digital Input SPI Clock OUT Analog Output Analog Output, PWM Output, OWI I/O SDAT/T2 6 Digital I/O SPI MISO/MOSI or Test2 T3 7 Digital I/O Test3 VSS 8 Ground Ground Family Members Part number MT601CT Description SOP-8 package, tubes packaging (3000pcs/bag) 2/ 1

3 3. Functional Description The MT601 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 delivers a voltage representation of the magnetic field at the surface of the IC. Figure 2 shows a simplified block diagram of the chip, consisting of the magnetic sensing element realized by two interleaved Wheatstone bridges to generate cosine and sine signals, gain stages, analog-to-digital converters (ADC) for signal conditioning, a digital signal processing (DSP) unit for angle calculation and digital-to-analog convert (DAC) to generate linear voltage output. Other supporting blocks such as LDO, NVM, I2C, etc. are also included. DSP LDO EEPROM OWI Communication OWI Magnetic Sensing Element G ADC Cordic Calibration DAC PWM OUT (Analog / PWM) G ADC Interpolator SPI Switch Output SO VSS Csn SCK SDAT Figure 2: Simplified System Block Diagram 3/ 1

4 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 V Positive Output Voltage 18 V Output Current 20 ma Reverse Output Voltage -0.3 V Reverse Output Current -0 ma Storage temperature C Operating Temperature C Magnetic Flux Density ± 1 T Electrostatic discharge (HBM) Norm: AEC-Q100-2 ± 4 kv. Electrical Characteristics Operating conditions: Ta= -40 to +10 C, = 4.-.V unless otherwise noted Symbol Parameter Conditions/Notes Min Typ Max Unit Supply Voltage V IDD Supply Current ma POR_LH POR Rising Level - V POR_HL POR Falling Level - V FS Clock Frequency Variation 4/ 1 Timing Spec Over all and Ta % FL Clock Frequency Drift Lifetime included % FR Analog Output Refresh Rate Slow mode Fast mode 4 8 KHz KHz FPWM PWM Frequency Hz TSTEP Step Response Time Exclude SlewRate Effect Slow mode, Filter=max Fast mode, Filter=min us us PS Phase Shift Slow mode, Filter=max Deg/Hz TSU SR Start-up Cycle Exclude SlewRate Effect Analog Output Slew Rate Slow mode Fast mode CL<=10nF CL<=100nF ms ms V/ms

5 Analog Output Spec IOUT Output Current analog output mode -1 1 ma ISHORT Output Short Circuit Current VOUT=0V VOUT=V VOUT=14V (Ta=2 ) ma ma ma RL Output Load Pull-down to Ground Pull-up to V KΩ KΩ VSAT_LO Analog Output Low Saturation Level Pull-up RL>=10KΩ Pull-up RL>=1KΩ % VSAT_HI Analog Output High Saturation Level Pull-down RL>=10KΩ Pull-down RL>=KΩ % CLAMP_LO Output Clamp Low Programmable 2 98 % Level CLAMP_HI Output Clamp High Programmable 2 98 % Level Digital Output Spec VOH Digital Output High Push-pull (Iout=20mA) 97 % Level VOL Digital Output Low Level Open-drain (RL=10KΩ) 1. % Push-pull (Iout=-20mA) SWH SW Output High Level Pull-up RL=1.KΩ V SWL SW Output Low Level Pull-up RL=1.KΩ V Trise Digital Output Rise Time Push-pull (RL=10KΩ, 2.2 Us CL=10nF) Tfall Digital Output Fall Time Open-drain or Push-pull 1.8 Us (RL=10KΩ, CL=10nF) Accuracy Spec INL Integral Non-Linearity Nominal condition -1 1 Deg INL_wc Integral Non-Linearity Worst-case air gap, Deg for Worst-case Magnet Placement off-axis misalignment INL_drift Integral Non-Linearity Full temperature range Deg temperature drift Anoi Input-referred Noise Slow mode, Filter=max Deg-rms Fast mode, Filter=min RE Ratiometry Error for % Analog Output VOS Analog Output Offset -1 1 % (Before Calibration) VOS_drift Analog Output Offset Temperature Drift % / 1

6 6. Magnetic Input Specification Operating conditions: Ta= -40 to +10 C, = 3.0-.V unless otherwise noted. Two-pole cylindrical diametrically magnetized source. Symbol Parameter Notes Min Typ Max Unit Dmag Diameter Recommended magnet: Ø8mm x 2.mm for cylindrical magnets mm Tmag Thickness mm Bpk Magnetic input field amplitude Measured at the IC surface Gauss AG Air Gap Magnet to IC surface distance mm RS Rotation Speed RPM DISP Displacement Radius Misalignment error between sensor center and magnet axis (Figure 3) mm TCmag1 Recommended NdFeB (Neodymium Iron Boron) %/ C TCmag2 magnet material and temperature drift SmCo (Samarium Cobalt) Figure 3: Magnet Arrangement 6/ 1

7 7. Description of End-User Programmable Items 7.1. Output Mode The MT680 output type is defined by the Output Mode and Switch Output Enable parameter Pin Parameter Value Description Output Mode Pin3 0 Analog Rail-to-Rail for C outmax =330nf 1 Low Side (NMOS) 2 High Side (PMOS) 3 Push-Pull Parameter Value Description Switch Output Enable 0 N/A 1 Switch Output Mode (Push-Pull) Analog Output Mode The Analog Output Mode is a rail-to-rail and ratio-metric output with a push-pull output stage configuration as shown in Figure 4. Clamp_High Clamp_low Degrees Analog Output Figure 4: Analog Output PWM Output Mode If PWM mode is enabled, the output signal is a digital signal with Pulse Width Modulation (PWM) as shown in Figure / 1 Figure : PWM Output

8 The PWM polarity is selected by the PWM POLARITY parameter Parameter Value Description 0 High level valid PWM POLARITY 1 Low level valid The PWM Frequency is selected by the PWM Frequency parameter Parameter Value PWM Frequency (Hz) PWM *The PWM frequency is subjected to the same tolerance as the system main clock Switch Output Mode If Switch Output Mode is selected, the output signal is a digital signal with the switch point selected by SW_OP parameter and hysteresis selected by SW_HYS parameter. SW HSY 0 SW Point 360 Switch Output Degrees Figure 6: Switch Output The Switch Output polarity is selected by the SW Output Polarity parameter. Parameter Value Description 0 Low level above SW_OP Switch Output Polarity 1 High level above SW_OP 7.2. Output Transfer Characteristic The transfer function of the MT601 from the digital angle value to the output voltage is defined by Clamp_high, Clamp_low and 4-Point parameters. Five segments can be programmed but the clamping levels are necessarily flat. 8/ 1

9 Output Angle(%) Clamp_high 1st Round 0~360 2nd Round 360~720 P4 P4 0 P3 P3 P2 P2 P1 P1 Clamp_low 0 DP 0 ~360 Calculated Angle (Degrees) Figure 7: Output Transfer Function Clockwise Parameter The CLOCKWISE parameter defines the magnet rotation direction. CW is defined by the reverse direction: pin order direction for SOP8. CCW is defined by the reverse direction: pin order direction for SOP Discontinuity Point (or Zero Degree Point) The Discontinuity Point defines the 0 point on the circle. The discontinuity point places the origin at any location of the trigonometric circle. The DP is used as reference for all the angular measurements Point Transfer Function Parameters The LNR parameters, together with the clamping values, fully define the relation (the transfer function) between the digital angle and the output signal. Output Angle(%) Clamp_high P4 Voltage_P4 Voltage_P3 Voltage_P2 Voltage_P1 Clamp_low P2 P1 Slop1 Slop2 0 Angle_P1 Angle_P2 Angle_P3 Angle_P4 360 P3 Slop3 Calculated Angle (Degrees) Figure 8: 4-Point Programmable Output Transfer Function 9/ 1

10 The transfer function of MT601 from the digital angle value to the output voltage is described by Figure 8. Five segments can be programmed but the clamping levels are necessarily flat. Two, three or four calibration points are then available, reducing the overall non-linearity of the IC by almost an order of magnitude each time. Four-point calibration solution will be preferred by customers looking for excellent non-linearity figures. Two-point calibration solution will be preferred by customers looking for a cheaper calibration set-up and shorter calibration time CLAMPING Parameters The clamping levels are two independent values to limit the output voltage range. The CLAMPLOW parameter adjusts the minimum output voltage level. The CLAMPHIGH parameter sets the maximum output voltage level. Both the parameters have 12bits of adjustments and the resolution is 0.024%. 10/ 1

11 8. 3-Wire SPI Interface CSN SCLK SDAT C[7] C[6] C[] C[4] C[3] C[2] C[1] C[0] D[7] D[6] D[] D[4] D[3] D[2] D[1] D[0] PC Figure 9: 3-Wire SPI Timing SPI data transfer starts when CSN is pulled low and stops when it is pulled high. SCLK is the Serial Port Clock and it is controlled by the SPI master, it is limited up to 12KHz. SDAT is the Serial Port Data Input and Output, and it is driven at the rising edge of CLK and should be captured at the falling edge of SCLK. C[7:0]: Read or Write Command Byte. C<7:0>=0xA, Master write data to MT601 C<7:0>=0xAF, Master read data from MT601 D[7:0]: Data PC : Parity Check Bit. MT601 sent out 8bit data and an extra parity check bit, but MT601 does not check the PC bit from master. For SDAT (Pin.6), when as data output, it is default NMOS open drain, but it could be programmed to push-pull. K 1 SDAT 6 100nf 8 VSS 4 SPI Master NC SCLK 3,7 CSN 2 MCU Figure 10: Reference Application Circuit for SPI 11/ 1

12 9. Recommended Application Diagrams 9.1. Reference Circuit Figure 9 shows a reference circuit for typical applications that use the analog output. For applications that use Switch Output, the reference circuit in Figure is recommended. R1 1 C4 C1 8 VSS 2,3,4,6,7 Output C C2 Out R2 Figure 11: Reference Application Circuit for Analog Interface Compact PCB Routing C1,C2 100nf Analog Out C1 100nf C2 4.7nf PWM Out Optimal EMC/EDS Performance C1,C2 1nf Close to IC Terminals C4,C 100nf Analog Out-Close to Connector C4 100nf C 4.7nf PWM Out-Close to Connector R1 10 Ω Not Recommended for Analog Out, Recommend for PWM Out R2 0 Ω Not Recommended for Analog Out, Recommend for PWM Out 100nf 1 8 VSS No Connection Switch Out 3 SO 2,4,6,7 4.7 nf 0 Ω Figure 12: Reference Application Circuit for Switch Output 12/ 1

13 9.2. Magnet Selection and Placement It is recommended that the magnetic field density at the chip surface reach 300 Gauss to guarantee that the magnetic sensing elements operate in saturation mode to ensure good linearity. Please be noted that the sensing element in the chip is not at the package center, rather it is aligned with PIN 3 and 6 edges (see the figures in the Package Information section). It is required that the magnet s center axis be aligned with the sensing element center. Any misalignment introduces additional angle error. Magnets with larger radius are more tolerant to off-axis misalignment. It also allows the magnet to be placed at the large air gap distance from the chip. 10. EEPROM Endurance Although the EEPROM is used for Calibration Data Storage, the MT601 embedded EEPROM is qualified to guarantee an endurance of minimum 1000 write cycles at 12 for engineering/calibration purpose. 13/ 1

14 11. Mechanical Angle Direction CW X CCW Y 0 degree 90 degree N S N S degree 270 degree N S N S / 1

15 11. Package Information (MT601) SOP-8 SENSING CENTER Y X Symbol Dimensions in Millimeters Dimensions in Inches Min Max Min Max A A A b c D E E e 1.270(BSC) 0.00(BSC) L θ x y / 1