MT6803 Magnetic Angle Sensor IC

Transcription

1 Features and Benefits Based on advanced magnetic field sensing technology Measures magnetic field direction rather than field intensity Contactless angle measurement Large air gap Excellent accuracy, even for weak magnetic field Position tolerant Negligible hysteresis Single chip solution RoHS Compliant 2011/65/EU Applications Contactless potentiometer Steering angle sensor for EPS Servo motor control General Description The MagnTek rotary position sensor MT6803 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/ 10

2 Pin Configuration Figure 1: Pin Configuration for SOP-8 Package (Also showing sensor element center location, zero degree position and angle rotation direction) Name Number Type Description MODE 1 Digital input Set to logic low in normal operation; Set to logic high in I 2 C mode. NSP 2 Digital input External magnetic switch input for 360 detection AOUT 3 Analog output Linear voltage output VDD 4 Supply 5V supply GND 5 Ground Ground HVPP 6 Supply 7.5V supply only needed for NVM programming. NC for normal operation. SCL 7 Digital I/O I 2 C clock SDA 8 Digital I/O I 2 C data Family Members Part number Description MT6803CT SOP-8 package, tubes packaging (3000pcs/bag) MTT6803CT SOP-8 package, tubes packaging (3000pcs/bag) MTT6803CT is qualified for automotive applications. 2/ 10

3 Functional Description The MT6803 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. A small low cost diametrically magnetized (two-pole) standard magnet can be used to provide angular position information. The MT6803 senses the orientation of the magnetic field and generates linear outputs as depicted in Figure 3. The output voltage amplitude is ratiometric to the supply voltage. 100% Figure 2: Simplified System Block Diagram Output Voltage (%VDD) 80% 60% 40% 20% 0% Angle (deg) Figure 3: Typical Output Waveform (Magnet rotates in clock-wise direction) 3/ 10

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 MT C Electrostatic discharge (HBM) MTT C MT ±2 kv MTT ±4 kv Electrical Characteristics Operating conditions: Ta= -40 to +150 C, VDD= V unless otherwise noted. Symbol Parameter Conditions/Notes Min Typ Max Unit VDD Supply Voltage V HVPP Supply Voltage V Idd Supply Current ma Sens Sensitivity Programmable %VDD/ Vsathi Output Saturation Voltage High Programmable %VDD Vsatlo Output Saturation Voltage Low Programmable %VDD LSB Analog Output Resolution 10-bit DAC %VDD INL Integral Non-Linearity Note (1) - ±1.0 ±2.0 Degrees Ta=25 C, VDD=3.3V, Anoi Output Noise RMS value, excluding %VDD DAC quantization noise Erm Ratiometric Error Note (2) % T PwrUp Power-up time ms T delay Propagation delay ms Analog Output Characteristics Rout Output Resistance Ω RL Pull-up or pull-down kω Output Load CL pf I 2 C IO Characteristics 4/ 10

5 V IH High level input voltage - VDD V V IL Low level input voltage V V SON Open Drain Output Saturation Voltage Iout = 3.3 ma V I LK Input Leakage Current ±1 μa I 2 C Timing Specification F scl SCL Clock khz t low SCL Low Period μs t high SCL High Period μs t sudat SDA Setup Time μs t hddat SDA Hold Time μs t hdsta Start Hold Time μs t susta Start Setup Time μs t susto Stop Setup Time μs t buf New Transmission Time μs Notes: 1. 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. 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 5V 100% 5 Magnetic Input Specification Operating conditions: Ta= -40 to +150 C, VDD= V unless otherwisenoted. Two-pole cylindrical diametrically magnetized source. Symbol Parameter Notes Min Typ Max Unit Dmag Diameter Recommended magnet: Ø8mm x 2.5mm for mm cylindrical magnets Tmag Thickness mm Bpk Magnetic input field amplitude Measured at the IC surface Gauss AG Air Gap Magnet to IC surface distance (Figure4) mm RS Rotation Speed KRPM DISP Off-Axis Misalignment error between Misalignment sensor center and magnet mm 5/ 10

6 axis (Figure4). TCmag1 Recommended NdFeB (Neodymium Iron magnet material Boron) TCmag2 and temperature drift SmCo (Samarium Cobalt) %/ C Figure4: Magnet Arrangement I 2 C Operation Alternative to the linear voltage output, the MT6803 also provides an I 2 C interface for host IC to read back angle information from its internal registers listed below. The slave address of the device is in 7-bit binary form. The read/write protocol is explained in details in this section. Address 0x03 0x04 Description Angle_Readback<7:0> Angle_Readback<15:8> Figure 5: I 2 C Timing Diagram Abbreviation MACK NACK RW Acknowledged by slave Acknowledged by master Not acknowledged by master Read/Write 6/ 10

7 Start/Stop/Ack START: Data transmission begins with a high to transition on SDA while SCL is held high. Once I 2 C transmission starts, the bus is considered busy. STOP: STOP condition is a low to high transition on SDA line while SCL is held high. ACK: Each byte of data transferred must be acknowledged. The transmitter must release the SDA line during the acknowledge pulse while the receiver mush then pull the SDA line low so that it remains stable low during the high period of the acknowledge clock cycle. NACK: If the receiver doesn t pull down the SDA line during the high period of the acknowledge clock cycle, it s recognized as NACK by the transmitter. I 2 C Write I 2 C write sequence begins with start condition generated by master followed by 7 bits slave address and a write bit (R/W=0). The slave sends an acknowledge bit (ACK=0) and releases the bus. The master sends the one byte register address. The slave again acknowledges the transmission and waits for 8 bits data which shall be written to the specified register address. After the slave acknowledges the data byte, the master generates a stop signal and terminates the writing protocol. Slave Address R W Register Address (0x09) Data (0x01) START STOP I 2 C Read I 2 C write sequence consists of a one-byte I 2 C write phase followed by the I 2 C read phase. A start condition must be generated between two phase. The I 2 C write phase addresses the slave and sends the register address to be read. After slave acknowledges the transmission, the master generates again a start condition and sends the slave address together with a read bit (R/W=1). Then master releases the bus and waits for the data bytes to be read out from slave. After each data byte the master has to generate an acknowledge bit (ACK = 0) to enable further data transfer. A NACK from the master stops the data being transferred from the slave. The slave releases the bus so that the master can generate a STOP condition and terminate the transmission. The register address is automatically incremented and more than one byte can be sequentially read out. Once a new data read transmission starts, the start address will be set to the register address specified in the current I 2 C write command. 7/ 10

8 START Slave Address R W Register Address (0x00) START Slave Address R W Data (0x00) MACK Data (0x01) D D D D D D D D D D D D D D D D Data Data MACK (0x02) D D D D D D D D MACK. MACK (0x07) D D D D D D D D NACK STOP. Application Information Reference Circuit Figure 6 shows a reference circuit for typical applications that use the analog output. For applications that use I 2 C interface to obtain angle information, the reference circuit in Figure 7 is recommended. For harsh working environment, it is recommended to add filtering (e.g. ferrite beads) and protection circuit (e.g. TVS) to the supply. Figure 6: Reference Application Circuit for Analog Interface 8/ 10

9 Figure 7: Reference Application Circuit for I 2 C Interface 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. 360 Degree Detection By default, MT6803 does not distinguish north and south pole, which makes its output have a period of 180 degrees. To enable 360 degree detection, it is possible to add external magnetic switch sensor devices such as Hall or GMR sensor to help it distinguish north and south pole. For details, please refer to application note AN001. Programming MT6803 can be programmed through dedicated programmer PB02 with its companion GUI software. The following parameters can be programmed: start angle, stop angle, sensitivity, output saturation (clamp) voltage, optional external magnetic switch sensor input, etc. 9/ 10

10 PACKAGE DESIGNATOR (MT6803CT) SOP-8 D b c L1' A A1 A2 E1 E L1 L e Symbol Dimensions in Millimeters Dimensions in Inches Min Max Min Max A A A b c D E E e 1.270(BSC) 0.050(BSC) L L REF 0.041REF L1-L x y z θ / 10