ADA4571R-EBZ User Guide UG-739 One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com ADA4571 End of Shaft Evaluation Board FEATURES GENERAL DESCRIPTION USB 2.0 interface Jumper for temperature compensation mode enable Jumper for power down mode enable Measurement test points and coaxial connectors The end of shaft evaluation system is composed of a Windows LabVIEW® GUI software, an ADA4571 motherboard, a magnetic stimulus mounted on top of a brushless dc motor, a daughter board with ADA4571 in its SOIC package, and a USB interface and controller board, the SDP-S. EVALUATION KIT CONTENTS ADA4571 magnetic stimulus: Dipole magnet Brushed or brushless dc motor with integrated control electronics Evaluation software CD-ROM (Windows® 7 32-bit and 64-bit compatible GUI) The motherboard features an on-board 5 V regulator, a 2-channel simultaneous sampling ADC and jumpers for enabling the temperature compensation and power-down modes within the ADA4571. The motherboard also features test points and unpopulated coaxial connectors for the three outputs of the device. The daughter board features the ADA4571 mounted above the magnetic stimulus as well as test points for the three outputs of the device. ADDITIONAL EQUIPMENT NEEDED Customer supplied 6 V to 12 V bench supply SDP interface board USB cable (supplied with SDP interface board) The SDP board is used to control the ADC on the motherboard and interface with the GUI. EVALUATION BOARD CONNECTION DIAGRAM 6V TO 12V SUPPLY USB SDP CONTROL CARD EVALUATION SYSTEM WITH MAGNETIC STIMULUS Figure 1. ADA4571 End of Shaft Evaluation System PLEASE SEE THE LAST PAGE FOR AN IMPORTANT WARNING AND LEGAL TERMS AND CONDITIONS. Rev. 0 | Page 1 of 13 12526-001 POWER SUPPLY PC GUI INTERFACE UG-739 ADA4571R-EBZ User Guide TABLE OF CONTENTS Features .............................................................................................. 1 Evaluation Board Hardware .............................................................4 Evaluation Kit Contents ................................................................... 1 Jumper Configuration ..................................................................4 Additional Equipment Needed ....................................................... 1 DUT Outputs .................................................................................4 General Description ......................................................................... 1 How to Use the Software ..................................................................5 Evaluation Board Connection Diagram ........................................ 1 Starting Up the Evaluation GUI ..................................................5 Revision History ............................................................................... 2 Overview of the Main GUI Window ..........................................6 Getting Started .................................................................................. 3 Evaluation Board Schematics and Artwork ................................ 12 Software Installation Procedures ................................................ 3 Related Links ................................................................................... 13 REVISION HISTORY 10/14—Revision 0: Initial Version Rev. 0 | Page 2 of 13 ADA4571R-EBZ User Guide UG-739 GETTING STARTED SOFTWARE INSTALLATION PROCEDURES SDP Installation There are two pieces of software to install: the Windows GUI and the SDP drivers. Next, install the Analog Devices, Inc., SDP driver. This driver allows the SDP control board to interface with the LabVIEW GUI. Windows GUI Installation 1. Use the following steps to install the GUI. 1. 2. Before connecting the USB cable or powering the board, insert the ADA4571-EBZ setup CD and from the installer directory, run the installer Setup.exe. When the Destination Directory screen appears (see Figure 2), click Next. Optionally, you may change the destination folder by clicking Browse, selecting a different destination folder, and clicking Next. When the SDP drivers setup wizard appears, click Next (see Figure 4). Figure 4. SDP Driver Installation 2. When the Choose Install Location screen appears (see Figure 5), click Next. Optionally, you may change the destination folder by clicking Browse, selecting a different destination folder, and clicking Next. Figure 2. Choose Destination Location 3. When the Start Installation window appears click Next to continue with the installation (see Figure 3). Figure 5. Choose Install Location 3. Figure 3. Review Installation 4. 4. Click Next to complete installation of the Windows LabVIEW GUI. Rev. 0 | Page 3 of 13 Click Finish to complete the installation of the SDP drivers. Connect the SDP control card to the motherboard and plug the SDP control card into the PC with the supplied USB cable. The computer now recognizes the SDP control board and the LabVIEW GUI may be opened to continue. UG-739 ADA4571R-EBZ User Guide EVALUATION BOARD HARDWARE The ADA4571 end of shaft demo evaluation system comprises of two boards (ADA4571 motherboard and ADA4571 daughter board) and a brushless dc motor. The ADA4571 evaluation system can be powered directly from the host PC USB or from an external bench supply. For maximum performance, it is recommended that an external bench power supply be used. JUMPER CONFIGURATION Refer to the ADA4571 motherboard schematic (see Figure 15) or the configuration panel to understand the purpose of each jumper. Configure the motherboard default jumper as follows (see Figure 15): When supplied directly from the host PC USB, the applied voltage is approximately 5 V. However, due to errors in the regulated USB voltage this value will vary and introduce extra errors into the system. To power the motherboard by an external bench supply, apply 6 V to 12 V to P7, the red terminal. When supplied by an external bench supply, the applied voltage is regulated to 5 V on the motherboard resulting in a better performance than powering directly from the host PC USB. If the bench supply features current-limiting, it is recommended to set the current limit to 100 mA, as a precaution. To power the motor by an external bench supply, 3 V to 9 V can be applied to P6, the blue terminal. The ground is shared with the ground of the motherboard. The speed of the brushless dc motor providing the magnetic stimulus to the ADA4571 is proportional to the voltage applied at this terminal. The attached motor provides a more constant rotational speed at lower applied voltages. Due to the LabVIEW GUI measuring the linearity of the outputs from the device, a more constant rotational speed is necessary to see the true performance of the ADA4571. See the Angular Error (Linearity) section for more information on motor performance. • • • Install the P9 and P10 jumpers in the standard position to connect the motor and board power to the external supply terminals. Install the P3 jumper connecting GC to VDD. This enables the gain control mode of the part. When P3 connects GC to GND, gain control mode is disabled. Install the P2 jumper connecting PD to GND. This disables the power-down mode of the part. When P2 connects PD to VDD, power-down mode is enabled and the ADA4571 outputs are put into a high impedance state. DUT OUTPUTS The outputs of the ADA4571 may be monitored at the test points located on the daughter board or the motherboard. The VSIN, VCOS, and VTEMP pins are all accessible on both of the boards. Rev. 0 | Page 4 of 13 ADA4571R-EBZ User Guide UG-739 HOW TO USE THE SOFTWARE STARTING UP THE EVALUATION GUI For maximum performance when the evaluation board is first powered up, control both the motor and the board using an external bench power supply. The jumper settings for P9 and P10 should be set for Ext Motor and Ext +5V as indicated on the board. Plug the positive supply for the board into the red terminal, P7, on the motherboard. This terminal requires 6 V to 12 V which is then regulated to 5 V on the motherboard using the on-board ADP3336. This supply powers both the on-board ADC, AD7866, as well as the daughter board containing the ADA4571. Plug the positive supply for the motor into the blue terminal, P6, on the motherboard. Due to mechanical nonlinearities of the dc motor, such as cogging during coil commuting, extra errors are introduced to the system at higher rotational velocities. For best performance, apply 3 V to Ext Motor terminal. If the motor supplied is a brushless dc motor; 3 V results in rotational speeds of approximately 2,000 RPM. Speeds up to 10,000 RPM are possible with a supply voltage of 12 V applied to this terminal. If the motor supplied is a brushed dc motor, 3 V results in rotational speeds of approximately 200 RPM. The nonidealities of the motor result in a higher reported nonlinearity of the device. This is an artifact of the motor and not the ADA4571. With an ideal magnetic stimulus, the ADA4571 has the same angular error performance regardless of rotational velocity. Rev. 0 | Page 5 of 13 UG-739 ADA4571R-EBZ User Guide OVERVIEW OF THE MAIN GUI WINDOW Initially all of the figures will be blank. To begin press Run (see Figure 6). The various output graphs are explained in detail in the following sections. Figure 6 shows the main GUI window, as it appears, after launching the GUI. When the program is first launched the SDP controller board must be recognized by the GUI before proceeding. Pressing Connect SDP reads the EEPROM ID of the motherboard to ensure the correct program is being used. If the SDP controller board is not connected or if the drivers are not installed correctly an error message will be shown. Ensure that the drivers are installed correctly if this occurs. After the SDP control board is properly connected and the program recognizes the motherboard, the Instructions tab appears. Click the Read tab to begin. There are two different categories of output waveforms as indicated by the GUI. The waveforms on the top of each tab, indicated as Uncorrected Plots, are without any post processing to correct for output offset before calculations are done on the raw data. In the case of the bottom waveforms, indicated as Offset Corrected Plots, the offset of each channel is subtracted from the raw data before completing any further calculations. These differences are discussed in further detail for each waveform in the Raw Waveforms section. Figure 6. ADA4571 Main Window Rev. 0 | Page 6 of 13 ADA4571R-EBZ User Guide UG-739 Raw Waveforms Arc Tangent2 (Magnetic Angle) The first figure is labeled Raw Waveforms (see Figure 11). This figure shows the sampled ADC raw data as the motor is spinning. The amplitude is shown in 12-bit code. The dual channel AD7866 simultaneously samples the sine and cosine channels at 100,000 samples per second. The internal 2.5 V reference of the AD7866 has been subtracted in hardware as the readout of the ADC is in twos complement. Therefore, the two signals are centered around zero in the raw waveform plot. The magnetic stimulus is sampled over many rotations and then cropped to three mechanical revolutions or six electrical revolutions. It is important that these two channels are simultaneously sampled or extra errors will be introduced from the phase delay between the sampling of the individual channels. The second set of figures are labeled ArcTangent (Magnetic Angle) (see Figure 8). These figures depict the calculated electrical angle of the ADA4571. This calculation is performed by the following equation: Angle = ArcTangent2(VSIN/VCOS) Because the two AMR bridges are deposited at a 45° relative angle, the sine and cosine outputs are 90° out of phase. This constant 90° phase difference results in the calculated angle over a constant rotary speed as a straight line. Normally the ArcTangent function will have a range of (−90° to +90°). However, if quadrant information is kept and corrected for after the calculation the second and third quadrant can be distinguished from the first and fourth. The function ArcTangent2 has this quadrant information and therefore the range is extended to (−180° to +180°). The program then zeros this waveform and therefore shows the angle between (0° and 360°). Figure 7. Raw Sine and Cosine Waveform There are two different figures shown depicting these sine and cosine waveforms. The uncorrected figure has not had any post processing applied and shows the absolute raw data from the sensor. For the offset corrected figure, the full three mechanical revolutions are averaged independently for both the sine and cosine channels giving the offset for the channel. These offset values are then subtracted from their respective channel to give the end waveform centered perfectly about zero. Note that when powering the board through a USB instead of by an external power supply there will be some variation in the supply voltage of the ADA4571. Due to the readout of the AD7866 being in twos complement form with respect to the internal 2.5 V reference, the offset of these waveforms will be higher than the inherent offset of the ADA4571. Figure 8. ArcTangent Calculation Plot The electrical angle period will repeat for every sinusoidal period of the sine and cosine outputs from the ADA4571. Just like the raw waveform data, three mechanical revolutions or six electrical revolutions are used for calculations. This results in six periods of angle information shown. The Uncorrected ArcTangent (Magnetic Angle) plot will have a slight bowed shape to it due to the sensor offset in the raw waveform. The Offset Corrected ArcTangent (Magnetic Angle) plot shows the angle information after the offset is nulled from each individual channel. This offset correction to the raw waveforms before the ArcTangent calculation results in a much more linear output plot. Rev. 0 | Page 7 of 13 UG-739 ADA4571R-EBZ User Guide Angular Error (Linearity) There are two different motors that may be supplied with your demo board: a brushless dc motor or a brushed dc motor. The brushed dc motor will introduce extra errors into the system due to cogging of the motor during rotation. To fully evaluate the performance of the sensor, an externally applied magnetic stimulus that has a smoother rotational velocity should be used with the supplied LabVIEW GUI. The third set of figures are labeled Angular Error (Degrees) (see Figure 6). This figure shows the linearity of the ArcTangent plot discussed in the Arc Tangent2 (Magnetic Angle) section. There is no encoder attached to the magnetic stimulus on the board and therefore the program cannot compare the calculated angle to the actual position of the magnet. Therefore, this plot is calculating the linearity of both the ADA4571 and the brushless dc motor providing the magnetic stimulus. Figure 10 shows the Offset Corrected Error (Degrees) plot. Large spikes appear in this plot due to the nonidealities of the magnetic stimulus. When the motor commutes, there is a kick from the excitation coils resulting in a higher reported linearity error at these points. The sensor measures the position of the magnetic stimulus and so these kicks during commuting will show up as an error from an ideal linear plot. This nonideality from the magnetic stimulus is more prevalent at higher speeds but is not a result of the sensor. The included motor is very smooth at lower speeds and, therefore, these spikes will not appear in the error plot. Due to the nonidealities of the brushless dc motor providing the magnetic stimulus, the reported angular error will always be higher than the actual error of the ADA4571. The motor provides a more constant rate of speed at lower rotational velocities and therefore the reported linearity will be lower at slower speeds. These extra errors are not indicative of the bandwidth of the ADA4571 as the part can handle motor rotational speeds as high as 50,000 RPM. Figure 9 shows the Uncorrected Angular Error (Degrees) plot. When powered by the host PC USB supply this waveform reports higher error than when powered by an external supply. This increased error is because the internal 2.5 V reference is subtracted in hardware from each ADC channel resulting in a higher inherent offset of the sensor if the supply voltage is not exactly 5 V. When powered by an external power source the ADA4571 supply is regulated to 5 V and, therefore, the ADC introduces no extra offset or errors to the system. Figure 9. Uncorrected Linearity Error Plot Rev. 0 | Page 8 of 13 Figure 10. Offset Corrected Linearity Error Plot ADA4571R-EBZ User Guide UG-739 Fourier Transform Radius Plot The fourth set of figures are labeled Fourier Transform. These figures show the spectral analysis of the two independent output signals. The fundamental frequency corresponds to the motor speed. Harmonics from the sensor are also depicted in this plot. The y-axis of this plot shows the magnitude of the frequency components. This value is the root mean squared (RMS), magnitude in 12-bit code of that specific frequency. The fifth set of figures are labeled Radius Check (see Figure 12). This figure plots the sine channel on the y-axis and the cosine channel on the x-axis. Both axes are shown in 12-bit codes. Due to the sinusoidal nature of the two channels and the 90° phase delay between the sine and cosine channels the plot is circular in nature. The x-axis is shown in hertz. The fundamental frequency shown depicts the electrical frequency. This will be two times the mechanical frequency. An example calculation for motor speed in RPM from a 100 Hz fundamental electrical frequency is shown as, The radius of this plot is constant throughout the entire rotation of the magnetic stimulus. The exact radius of this plot is inversely proportional to the temperature of the ADA4571. At lower device temperatures, the radius increases while at higher device temperatures the radius decreases; when held at a constant temperature the radius will also be constant. 100 Hz × (1 electrical cycle)/(2 mechanical cycles) × (60 seconds)/(1 minute) = 3,000 RPM Figure 11. Spectral Output for Sine and Cosine Channels Due to the layout of the AMR bridge odd harmonics which are usually present in the output of sensors, such as third and fifth, are suppressed. Spectral analysis of the sensor can be useful for debuging purposes. Even harmonics appear in this plot when there is gross misalignment between the center of the AMR sensor and the magnetic stimulus. Figure 12. Radius Plot of Output Waveforms The temperature dependent variation in output amplitude of the AMR bridge is due to the reduced change in resistance of the AMR film at higher temperatures. The ADA4571 provides an internal regulated voltage to the AMR bridge supply. By enabling the temperature compensation mode of the ADA4571, this regulated supply voltage varies with temperature. At higher temperatures, the regulator provides a higher bridge supply voltage, thus increasing the output amplitude of the device. Using this mode, the output amplitude and, therefore, radius in this plot will be more consistent over the wide temperature range of −40°C to 150°C. This mode is enabled by default by an internal pull-up resistor on the GC pin. Moving Jumper P3 to the correct position as outlined in Figure 14 and Figure 15 will disable the temperature compensation mode of the device. There is an internal temperature sensor on the ADA4571 that is used to adjust the bridge supply voltage. The internal temperature sensor voltage is available to the end user and can be monitored on the daughter board or the motherboard as outlined in Figure 14 and Figure 15. Rev. 0 | Page 9 of 13 UG-739 ADA4571R-EBZ User Guide Figure 13. ADA4571 Part Diagnostics Tab Rev. 0 | Page 10 of 13 ADA4571R-EBZ User Guide UG-739 Figure 14. ADA4571 Board Configuration Tab Rev. 0 | Page 11 of 13 UG-739 ADA4571R-EBZ User Guide EVALUATION BOARD SCHEMATIC Figure 15. ADA4571 Evaluation Motherboard Schematic Rev. 0 | Page 12 of 13 ADA4571R-EBZ User Guide UG-739 RELATED LINKS Resource ADA4571 ADP3336 AD7866 Description Product Page, ADA4571 Integrated AMR Angle Sensor and Signal Conditioner Product Page, High Accuracy Ultralow IQ, 500 mA anyCAP® Adjustable Low Dropout Regulator Product Page, Dual 1 MSPS, 12-Bit, 2-Channel SAR ADC with Serial Interface ESD Caution ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality. Legal Terms and Conditions By using the evaluation board discussed herein (together with any tools, components documentation or support materials, the “Evaluation Board”), you are agreeing to be bound by the terms and conditions set forth below (“Agreement”) unless you have purchased the Evaluation Board, in which case the Analog Devices Standard Terms and Conditions of Sale shall govern. Do not use the Evaluation Board until you have read and agreed to the Agreement. Your use of the Evaluation Board shall signify your acceptance of the Agreement. This Agreement is made by and between you (“Customer”) and Analog Devices, Inc. (“ADI”), with its principal place of business at One Technology Way, Norwood, MA 02062, USA. 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