AD7746 Evaluation Board EVAL-AD7746EB Data Sheet FEATURES AD7746 DEVICE DESCRIPTION Full-featured evaluation board for the AD7746 PC evaluation software for control and measurement of the AD7746 USB interface and cable in kit The AD7746 is a high resolution capacitance-to-digital converter (CDC). The capacitance to be measured is connected directly to the device inputs. The architecture features inherent high resolution (24 bits, no missing codes, up to 21-bit effective resolution), high linearity (0.01%), and high accuracy (±4 fF factory calibrated). The AD7746 capacitance input range is ±4 pF (changing); the AD7746 can accept up to 17 pF common-mode capacitance (not changing), which can be balanced by a programmable on-chip digital-to-capacitance converter (CAPDAC). APPLICATIONS Capacitive length sensor demo AD7746 performance evaluation Platform to integrate the AD7746 into system design EVALUATION BOARD DESCRIPTION The AD7746 has two capacitive input channels. Each channel can be configured as single-ended or differential. The AD7746 is designed for floating capacitive sensors. For capacitive sensors with one plate connected to ground, the AD7747 is recommended. This data sheet describes the evaluation board for the AD7746. The evaluation board interfaces to the USB port of a PC. Evaluation software is available with the evaluation board, which allows the user to easily communicate with the AD7746. The AD7746 has an on-chip temperature sensor with resolution of 0.1°C and accuracy of ±2°C. The on-chip voltage reference and the on-chip clock generator eliminate the need for any external components in most capacitive sensor applications. The part has a standard voltage input, which, together with the differential reference input, allows easy interface to an external temperature sensor such as an RTD or diode. Note that the AD7746 evaluation board software should be installed before connecting the AD7746 evaluation board to the PC. To properly use the evaluation board, see the AD7746 data sheet on the Analog Devices, Inc., website. You can download the data sheet from www.analog.com/AD7746. FUNCTIONAL BLOCK DIAGRAM CAPACITIVE LENGTH SENSOR DEMO EXT CIN2(–) CYPRESS EZ USB SDA SCL RDY 05513-001 EEPROM (USB ID) VREF 0W CIN1(–) USB VIN AD7746 I2C EXCB PC + LABVIEW USER SOFTWARE 3.3V EXCA ADP3303 VOLTAGE REGULATOR CIN2(+) AVDD 5.0V CIN1(+) OPTIONAL EXT. AVDD Figure 1. Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2005–2011 Analog Devices, Inc. All rights reserved. EVAL-AD7746EB Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Evaluation Board Software ...............................................................6 Applications ....................................................................................... 1 Configuring the Evaluation Board ..............................................6 Evaluation Board Description......................................................... 1 Getting Started with the Software ...............................................6 AD7746 Device Description ........................................................... 1 Setup Window ...............................................................................8 Functional Block Diagram .............................................................. 1 User Unit Setup..............................................................................9 Revision History ............................................................................... 2 Performing a Noise Analysis..................................................... 10 Evaluation Board Software Installation ......................................... 3 Saving and Reloading User Configurations.............................. 10 Evaluation Board Hardware ............................................................ 4 Schematics and Artwork ............................................................... 11 Power Supplies .............................................................................. 4 Component ID ............................................................................ 12 I C Interface Configuration Options ......................................... 4 Ordering Information .................................................................... 13 USB Connector ............................................................................. 5 Bill of Materials ........................................................................... 13 Sockets ........................................................................................... 5 Ordering Guide .......................................................................... 13 2 ESD Caution................................................................................ 13 REVISION HISTORY 11/11—Rev. 0 to Rev. A Changes to Evaluation Board Software Installation Section ...... 3 Deleted Figure 2 ................................................................................ 3 Added Figure 2, Figure 3, and Figure 4; Renumbered Figures Sequentially ......................................................................... 3 Renamed Evaluation Board Hardware and Interfacing Section to Evaluation Board Hardware Section ......................................... 4 Changes to Power Supplies Section................................................ 4 Deleted Link Options Section, Figure 3, and Table 1 .................. 4 Added I2C Interface Configuration Options Section, Figure 6, Figure 7, and Figure 8 ...................................................... 4 Deleted Connecting the Board to the PC Section ........................5 Renamed Schematic Section to Schematics and Artwork Section; Changes to Figure 10....................................................... 11 Renamed Layout Section to Component ID Section ................ 12 Added Ordering Information Section, Bill of Materials Section, and Table 2........................................................................ 13 Changes to Ordering Guide .......................................................... 13 5/05—Revision 0: Initial Version Rev. A | Page 2 of 16 Data Sheet EVAL-AD7746EB EVALUATION BOARD SOFTWARE INSTALLATION Before connecting the AD7746 evaluation board to the PC, install the AD7746 evaluation board software by completing the following steps. 1. 3. Insert the AD7746 evaluation kit CD into the CD-ROM drive of your PC. Connect the AD7746 evaluation board to the USB connector of the PC using the USB cable included in the evaluation kit. The POWER LED on the evaluation board turns on, and the Found New Hardware Wizard starts automatically on the PC (see Figure 4). AD7746 Evaluation Board Please install software before connecting board to USB port! Version 2.2 Feb. 2011 05513-104 Evaluation kit documentation including installation guideline may be found in file AD7746EB.pdf on this CD AD7746 Figure 4. Found New Hardware Wizard Evaluation Kit CD 05513-002 4. d. Figure 2. AD7746 Evaluation Kit CD Follow the steps in the Found New Hardware Wizard window. If a message that the software has not passed Windows® Logo testing appears, click Continue Anyway (see Figure 5). 05513-103 05513-003 The evaluation software installation wizard should start automatically (see Figure 3). If the wizard does not start, run Setup.exe from the AD7746 evaluation kit CD. Figure 3. AD7746 Evaluation Software Installation Wizard 2. Figure 5. Windows Logo Warning 5. Follow the steps in the evaluation software installation wizard until the installation is completed. Rev. A | Page 3 of 16 Follow the steps in the Found New Hardware Wizard window until the installation is completed. EVAL-AD7746EB Data Sheet EVALUATION BOARD HARDWARE POWER SUPPLIES External Connection—USB The board is powered via the 5 V supply from the USB connector, J1, indicated via LED D1 (POWER). The 5 V supply can be used to power the AD7746 directly. A 3.3 V regulated voltage from the on-board ADP3303 high precision, low power, 3.3 V output voltage regulator can also be used. Alternatively, the AD7746 can be powered using an external 3 V or 5 V power supply via J2. The AD7746 evaluation board allows customers to connect their own specific AD7746 application board to Pin 4, Pin 6, and Pin 8 of LK2. Using the PC evaluation software, customers can evaluate their application hardware using the AD7746 evaluation board as a USB-to-I2C digital interface only, as shown in Figure 7. I2C INTERFACE CONFIGURATION OPTIONS AD7746 EVALUATION BOARD The AD7746 evaluation board allows different digital interface configurations by redirecting the I2C signals, SDA and SCL, on LK2. U1 U3 MICROCONTROLLER Default Configuration SDA SCL AD7746 RDY Links in the SDA, SCL, and RDY positions of LK2 connect the USB microcontroller as the I2C bus master to the on-board AD7746, as shown in Figure 6. This configuration allows easy use of the evaluation board, together with the PC software. LK2 FINAL APPLICATION AD7746 EVALUATION BOARD SDA U1 MICROCONTROLLER SCL SDA SCL AD7746 05513-107 U3 RDY AD7746 Figure 7. AD7746 Evaluation Board as USB-to-I2C Interface RDY The AD7746 evaluation board can be used for software development by connecting a customer-specific external microcontroller board to Pin 3, Pin 5, and Pin 7 of LK2, as shown in Figure 8. In this configuration, the AD7746 CDC on the evaluation board is used as the sensing device. AD7746 EVALUATION BOARD U1 U3 MICROCONTROLLER SDA SCL AD7746 RDY LK2 CUSTOMER BOARD SDA MICROCONTROLLER SCL RDY 05513-108 Figure 6. AD7746 Evaluation Board in Default Configuration 05513-106 LK2 External Connection—AD7746 Figure 8. AD7746 Evaluation Board Software Development Platform Rev. A | Page 4 of 16 Data Sheet EVAL-AD7746EB USB CONNECTOR SOCKETS A standard USB connector, J1, is used to connect the evaluation board to the USB port of a PC. A standard USB connector cable is included with the AD7746 evaluation kit. Because the board is powered by the USB connector, an external power supply is not required, although one can be connected to J2. The AD7746 evaluation board has four populated sockets: EXCA (P1), EXCB (P2), CIN1− (P3), and CIN1+ (P4). The functions of these sockets are described in Table 1. Communication between the AD7746 evaluation board and the PC is over the USB interface. The on-board USB controller controls this communication. To interface to the AD7746 using the analog voltage input channel or the external temperature sensor and an external voltage reference, use the unpopulated through hole pads labeled AIN+, AIN−, REF+, and REF− located on the AD7746 evaluation board. Table 1. Socket Functions Socket CIN1+ CIN1− CIN2+ 1 CIN2−1 EXCA EXCB 1 Function Subminiature BNC (SMB) connector. The capacitive input signal for the CIN1(+) input of the AD7746 is applied to this socket. Subminiature BNC (SMB) connector. The capacitive input signal for the CIN1(−) input of the AD7746 is applied to this socket. Subminiature BNC (SMB) connector. The capacitive input signal for the CIN2(+) input of the AD7746 is applied to this socket. On this evaluation board, the positive terminal of the capacitive length sensor demo is connected to CIN2+. Subminiature BNC (SMB) connector. The capacitive input signal for the CIN2(−) input of the AD7746 is applied to this socket. Subminiature BNC (SMB) connector. This socket is connected to the EXCA output of the AD7746. On this evaluation board, the negative terminal of the capacitive length sensor demo is connected to EXCA. This provides excitation to the on-board capacitive length sensor demo. Subminiature BNC (SMB) connector. This socket is connected to the EXCB output of the AD7746. The CIN2− and CIN2+ sockets (P5 and P6, respectively) are unpopulated on the AD7746 evaluation board. Rev. A | Page 5 of 16 EVAL-AD7746EB Data Sheet EVALUATION BOARD SOFTWARE CONFIGURING THE EVALUATION BOARD The evaluation board is initially configured to allow the user to interface any capacitive input directly to CIN1 of the AD7746 device. To do this, connect one end of the capacitive input to the SMB connector labeled CIN1+ or CIN1−. Then connect the other end of the capacitive input to the SMB connector labeled EXCB. The AD7746 provides a second capacitive channel, CIN2. On the AD7746 evaluation board, the second capacitive channel is used with the on-board capacitive length sensor demo. GETTING STARTED WITH THE SOFTWARE To run the AD7746 evaluation board software, follow these steps: 1. From the Start menu, select Program Files > Analog Devices\AD7746 Evaluation Software. The AD7745/AD7746 Evaluation Software window appears (see Figure 9). By default, the application opens to the Real Time tab. 2. Click the Length Demo (CH2) button. This action enables continuous conversions on Capacitive Channel 2 in singleended mode, enables EXCA as the excitation output pin, sets the update rate, and initializes CAPDAC A. The Capacitive Length Sensor Demo window appears (see Figure 10). 05513-004 To disable the capacitive length sensor demo, disconnect the two 0 Ω SMD resistors, R1 and R2. Any capacitive sensor can then be directly interfaced to CIN2 of the AD7746 by connecting one end of the capacitive input to either of the SMB connectors labeled CIN2+ or CIN2− and the other end to one of the SMB connectors labeled EXCA or EXCB. Note that after the capacitive length sensor demo is disabled, either of the excitation output pins (EXCA or EXCB) can be used as the excitation source, regardless of which capacitive channel is enabled. These settings are configurable using the evaluation board software. Figure 9. AD7745/AD7746 Evaluation Software Window Rev. A | Page 6 of 16 Data Sheet 4. Slide the ruler on the evaluation board. This action is mirrored on the screen. The code, capacitance, and length (in inches or mm) appear on the right side of the window (see Figure 10). These values change as you slide the ruler on the evaluation board. Remove the ruler completely by clicking the 0 mm/0 inch Cal button. 5. 6. Place the ruler at the 51 mm/2 inch mark by clicking the 51 mm/2 inch Cal button. The part is now calibrated to the length of the ruler. Note that when the ruler length exceeds 80 mm, the demo can no longer measure the ruler length because the input capacitance range (±4 pF) has been exceeded. Click BACK to return to the Real Time tab. 05513-005 3. EVAL-AD7746EB Figure 10. Capacitive Length Sensor Demo Window Rev. A | Page 7 of 16 EVAL-AD7746EB Data Sheet Note that the Setup window reflects the settings established during the capacitive length sensor demo, that is, SETUP WINDOW After running the capacitive length sensor demo to check the settings and familiarize yourself with the software, follow these steps to set up the software. On the Real Time tab, click Setup. The Setup window appears (see Figure 11). The Setup window allows you to configure the capacitive channel, the voltage/temperature channel, the output pin for the excitation source, the CAPDACs, and the AD7746 operating mode. • 2. Capacitive Channel 2 is enabled in single-ended mode. EXCA is enabled as the excitation output pin. CAPDAC A is set to a value determined by the demo calibration routine. The part is in continuous conversion mode. Click OK to return to the Real Time tab. 05513-006 1. • • • Figure 11. Setup Window Rev. A | Page 8 of 16 Data Sheet EVAL-AD7746EB USER UNIT SETUP To set up the user unit, follow these steps. 1. On the Real Time tab, click User Unit Setup. The User Unit Setup window appears (see Figure 12). The User Unit Setup window allows you to configure a unit that reflects the nature and sensitivity of the capacitive sensor connected to the selected capacitive input. This configuration is then reflected in the Real Time tab and the Analysis tab. After the capacitive length sensor demo is run, the user unit reflects the capacitive length sensor by default. Click OK to return to the Real Time tab. Click START. Note that the Real Time tab reflects the settings established during the capacitive length sensor demo. The samples collected are displayed graphically in real time. For complete information about this setup, click Setup. Alternatively, you can click Registers. This action displays a detailed register map of all available registers and reflects the current user settings. The Registers window can be used if a more detailed configuration of the AD7746 device is required. 05513-007 2. 3. 4. 5. The samples are also displayed in hexadecimal format and capacitance. When you move the ruler, the tab is updated in real time, and the input capacitance changes. Also, the User Unit field displays the length of the ruler in mm. Click STOP to stop the display of data. Click Quick Setup (CH1). This action enables Capacitive Channel 1, enables EXCB as the excitation output pin, and places the part in continuous conversion mode. In continuous conversion mode, the part directly measures any capacitance placed across the CIN1(+)/CIN1(−) and EXCB pins. Figure 12. User Unit Setup Window Rev. A | Page 9 of 16 EVAL-AD7746EB Data Sheet A summary of the current configuration as well as the data for the selected number of samples in hexadecimal format is saved to the file. PERFORMING A NOISE ANALYSIS With the quick setup for Capacitive Channel 1 still in place, click the Analysis tab. The Analysis window appears (see Figure 13). To perform a noise analysis, follow these steps. 1. SAVING AND RELOADING USER CONFIGURATIONS Type the number of samples required and click START. After the samples are collected, they can be displayed as a waveform or as a histogram. The average, RMS noise, p-p noise, RMS resolution, and p-p resolution values relating to the collected set of samples appear in the Analysis (Codes) box on the right side of the window. These values can be displayed in code, in capacitance, or in the user configured unit. 3. To save this set of collected samples, select File > Save Binary Data. Select the directory and file name where you want to save the data. The default file name is Binary Data.txt. 1. 2. Select File > Save Settings. Select the directory and file name where you want to save the current user configuration. The default file name is Settings.txt. The user unit, user offset, and user range are saved together with the complete register map as it appears in the Registers window. To reload these settings at any time, select File > Load Settings. A prompt appears and points, by default, to the previously saved user configuration Settings.txt file. 05513-008 2. You can save a configuration and reload it at a later time. To save any configuration, follow these steps: Figure 13. Analysis Window Rev. A | Page 10 of 16 CIN1+ CIN1– EXCB EXCA DEMO_EXC R1 AGND J2–2 P4 P3 P2 P1 100mm 8 7 6 5 4 3 2 1 D3 S2A VDD EXCA CLAMP CIN1(+) CIN2(+) CIN1(–) CIN2(–) REFIN(–) VIN(+) REFIN(+) VIN(–) GND NC RDY EXCB SDA AD7746 SCL U1 C A B 9 10 11 12 13 14 15 16 1.4pF 3 4 1 2 R6 1R5 R3 R4 R5 R2 P6 P5 0Ω C1 + 0.1µF 0Ω 0Ω 0Ω 1 3 5 7 9 AVDD RDY SCL SDA DEMO_CIN DEMO_EXC DEMO_CIN CIN2+ C13 0.1µF LK2 RDY SCL SDA +3.3V 2 4 6 8 10 DGND D2 RED 0.1µF C15 +3.3V POWER 45 46 47 48 49 50 51 52 33 34 35 36 37 38 39 40 18 19 20 21 22 23 24 25 15 16 PD0/FD8 PD1/FD9 PD2/FD10 PD3/FD11 PD4/FD12 PD5/FD13 PD6/FD14 PD7/FD15 0.1µF C16 C17 0.1µF C18 0.1µF C10 0.1µF 0.1µF C19 4 5 0.1µF C20 0.1µF C21 54 CLKOUT 31 CTL2/*FLAGC 30 CTL1/*FLAGB 29 CTL0/*FLAGA 42 RESET 44 *WAKEUP 13 IFCLK 14 RSVD 2 RDY1/*SLWR 1 RDY0/*SLRD U3 CY7C68013 XTALOUT XTALIN D– D+ 9 8 8 7 5 6 0.1µF C22 10µF + C23 C9 10µF HOST C14 0.1µF C5 1µF R12 100kΩ +3.3V R11 4 GND SYSTEM 5 SH 6 SH D+ 1 VCC 2 D– 3 J1 USB–B R14 100kΩ +3.3V R13 100kΩ +5V + C11 0.1µF +5V C7 12pF 24MHz C6 12pF Y1 USB INTERFACE U2 ADP3303 IN IN SD GND ERR 1 OUT 2 OUT 3 NR 4 3.3V DVDD REGULATOR USB CONTROLLER PA0/INT0 PA1/INT1 PA2/*SLOE PA3/*WU2 PA4/FIF0ADR0 PA5/FIF0ADR1 PA6/*PKTEND PA7/*FLAGD/SLCS PB0/FD0 PB1/FD1 PB2/FD2 PB3/FD3 PB4/FD4 PB5/FD5 PB6/FD6 PB7/FD7 SCL SDA DECOUPLING FOR U2 R7 1kΩ D1 GREEN +3.3V FUNC. R8 1kΩ +3.3V I2C INTERFACE +3.3V C8 10µF +3.3V + R10 2.2kΩ +3.3V R9 2.2kΩ +3.3V I2C TERMINATION OPTIONAL INTERFACE CONSTANTS AGND CIN2– +3.3V U4 24LC64 8 VCC 7 WP 6 SCL 5 GND SDA 1 2 A0 A1 3 A2 4 +3.3V EEPROM FOR USB CONSTANTS GROUND CONNECTION C3 1µF C2 10µF OPTIONAL INTERFACE FILTER AVDD AVDD C4 1µF L1 0.5µH CAPACITIVE LENGTH SENSOR DEMO 0Ω C12 0.1µF LK1 AVDD AGND 6 EXT.VDD J2–1 T1 AGND T2 REF– T3 REF+ T4 AIN– T5 AIN+ T6 AVDD 3 AVCC 7 11 17 27 32 43 55 AVCC VCC VCC VCC VCC VCC VCC AGND GND GND GND GND GND GND Rev. A | Page 11 of 16 10 12 26 28 41 53 56 Figure 14. Evaluation Board Schematics 05513-009 AVDD SELECT: A EXT.VDD B +5.0V C +3.3V +3.3V +5V Data Sheet EVAL-AD7746EB SCHEMATICS AND ARTWORK EVAL-AD7746EB Data Sheet 05513-010 COMPONENT ID Figure 15. Evaluation Board Layout, Silkscreen Rev. A | Page 12 of 16 Data Sheet EVAL-AD7746EB ORDERING INFORMATION BILL OF MATERIALS Table 2. Qty 3 1 1 1 1 1 1 14 4 3 2 5 1 2 2 3 1 1 1 1 4 1 1 4 Designator U1, Sample1, Sample2 U2 U3 U4 D1 D2 D3 C1, C10 to C22 C2, C8, C9, C23 C3 to C5 C6, C7 R1 to R5 R6 R7, R8 R9, R10 R12 to R14 L1 Y1 J1 J2 P1 to P4 LK1 LK2 Jumper socket Description CDC for proximity sensing, 16-lead TSSOP 3.3 V voltage regulator, low IQ, 8-lead SOIC Microcontroller, EZ-USB FX2LP, 56-lead QFN EEPROM, I2C, 64 kb, 8-lead SOIC LED, green, 15 mcd, 572 nm, 0805 LED, red, 10 mcd, 626 nm, 0805 Diode, 50 V, 1.5 A, SMB Capacitor, ceramic, SMD, 100 nF, X7R, 16 V, 0603 Capacitor, tantalum, SMD, 10 μF, 6.3 V, TAJ-A Capacitor, ceramic, SMD, 1 μF, Y5V, 10 V, 0603 Capacitor, ceramic, SMD, 12 pF, NP0, 50 V, 0603 Resistor, SMD, 0 Ω, 0603 Resistor, SMD, 1.5 Ω, 1%, 0603 Resistor, SMD, 1 kΩ, 1%, 0603 Resistor, SMD, 2.2 kΩ, 1%, 0603 Resistor, SMD, 100 kΩ, 1%, 0603 Ferrite bead, SMD, 300Z, 200 mA, 0805 Crystal, 24 MHz, 12 pF, CMS-8 series Connector, USB type Mini-B Terminal block with screws, pitch 5 mm Connector, SMB, 50 Ω Straight header, 2 × 3-pin, pitch 2.54 mm Straight header, 2 × 5-pin, pitch 2.54 mm Jumper socket, red; insert in these locations: LK1 (5.0 V), LK2 (SDA, SCL, RDY) ESD CAUTION ORDERING GUIDE Model EVAL-AD7746EBZ1 1 Manufacturer Analog Devices Analog Devices Cypress Microchip Avago Avago Vishay AVX AVX Yageo Yageo Multicomp Multicomp Multicomp Multicomp Multicomp Sigma Inductors ECS Molex Camden Multicomp Harwin Harwin Harwin Description Evaluation Board Z = RoHS Compliant Part. Rev. A | Page 13 of 16 Part No. AD7746RUZ ADP3303ARZ-3.3 CY7C68013A-56LFXC 24LC64-I/SN HSMG-C170 HSMS-C191 S2A-E3/52T CM105X7R104K16AT TAJA106K006RNJ CC0603ZRY5V6BB105 CC0603JRNPO9BN120 MC 0.063W 0603 0R MC 0.063W 0603 1% 1R5 MC 0.063W 0603 1% 1k MC 0.063W 0603 1% 2k2 MC 0.063W 0603 1% 100k BMB2A0300AN1 ECS-240-12-20A-TR 56579-0576 CTB5000/2 24-14-2-TGG M20-9980346 M20-9980546 M7566-05 EVAL-AD7746EB Data Sheet NOTES Rev. A | Page 14 of 16 Data Sheet EVAL-AD7746EB NOTES Rev. A | Page 15 of 16 EVAL-AD7746EB Data Sheet NOTES I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors) ©2005–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. EB05513-0-11/11(A) Rev. A | Page 16 of 16