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| = FEATURES Evaluation Board for 12-bit high speed, low power, successive-approximation ADC EVAL-AD7492CB Interfacing to this board is through a 96-way connector. This 96-way connector is compatible with the EVAL-CONTROL BRD2 which is also available from Analog Devices. External sockets are provided for the CONVST input and the VIN inputs. OPERATING THE AD7492 EVALUATION BOARD Power Supplies Full-Featured Evaluation Board for the AD7492 EVAL-CONTROL BRD2 Compatible Stand Alone Capability On-Board Analog Buffering and Reference Optional On-Board Analog Bias-Up Circuit Various Linking Options PC Software for Control and Data Analysis when used with EVAL-CONTROL BRD2 When using this evaluation board with the EVAL-CONTROL BRD2, all supplies are provided from the EVALCONTROL BRD2 through the 96 way connector. When using the board as a stand alone unit, external supplies must be provided. This evaluation board has five power supply inputs: VDD, AGND, VSS, VDRIVE and DGND. +5 V must be connected to the VDD input to supply the AVDD and DVDD pins on the AD7492, the AD780 voltage reference, the positive supply pin of all three op-amps and the digital control logic. 0 V is connected to the AGND input. -5 V must be connected to the VSS input to supply the negative supply pins on all three op-amps. The VDRIVE input can be used to provide an external voltage for the output drivers on the AD7492. If an external VDRIVE is supplied, it is referenced to the DGND input which should be tied to 0 V. The supplies are decoupled to the relevant ground plane with 47F tantalum and 0.1F multilayer ceramic capacitors at the point where they enter the board. The supply pins of the op-amps and INTRODUCTION This Technical Note describes the evaluation board for the AD7492 12-bit, high speed, low power, internal reference and clock, successive approximation A/D converter that operates from a single 2.7 V to 5.25 V supply. Full data on the AD7492 is available in the AD7492 data sheet available from Analog Devices and should be consulted in conjunction with this Technical Note when using the Evaluation Board. On-board components include an AD780 which is a pin programmable +2.5 V or +3 V ultra high precision bandgap reference, two AD797 op-amps used to buffer the analog input, and an OP07 op-amp used to buffer the DC bias voltage applied to the optional analog input bias-up circuit. There are various link options which are explained in detail on page 2. FUNCTIONAL BLOCK DIAGRAM Unipolar Ain Buffe r AD7492 ADC Vin Bipolar Ain Bia s-u p buff er Co ntrol Lines External Re fe ren ce Ref O ut Pow er Supply Circuit 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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703 96 Pin Ev al-Control Board Interface Data B u s EVAL-AD7492CB reference are also decoupled to AGND with a 10F tantalum and a 0.1F ceramic capacitor. The AD7492 AVDD supply pin is decoupled to AGND with 10uF tantalum and 0.1F multilayer ceramic capacitors. The AD7492 DVDD and VDRIVE pins are decoupled to AGND with 10uF tantalum capacitors and to DGND with 0.1F multilayer ceramic capacitors. Extensive ground planes are used on this board to minimize the effect of high frequency noise interference. There are two ground planes, AGND and DGND. These are connected at one location close to the AD7492. Analog Input Section The analog input section of this evaluation board accommodates unipolar and bipolar signals. Unipolar signals within the AD7492 analog input signal range of 0 V - 2.5 V are connected via SK1. They are then buffered by the on-board buffer before being applied to the VIN pin of the AD7492. Bipolar signals are connected via SK3 and are biased up by the on-board biasup buffer circuit before being applied to the VIN pin of the AD7492. The input impedence of the bias-up circuit is 50 which is determined by the value of R7. The input impedence may be modified by removing/changing the value of R7. To obtain optimum performance from this evaluation board the use of an impedence matched, passive filter is recommended before the analog signal is applied to the evaluation board. For example, when using a 100KHz input tone, a 100KHz 50 filter from TTE (part number KC5-100K-15K-50/50-720B) is suitable. R13 Potentiometer (50Kohm) This variable resistor is used to trim the DC bias voltage applied to the optional analog input bias-up circuit. This bias voltage is factory preset to 1.25 V which biases a bipolar signal to swing around the midpoint of the analog input range (0 - 2.5 V). If any adjustment is required, the user can use the histogram window in the eval-board software to analyze the DC voltage variation while adjusting the trim pot. To view this properly, an analog input signal should not be applied to the board. Under normal operation this pot should not be adjusted as it is preset for optimum performance. LINK AND SWITCH OPTIONS There are 12 link options which must be set for the required operating setup before using the evaluation board. The functions of these options are outlined below. Link No. Function. LK1 This link is used to select the DC bias voltage to be applied to the optional Vin bias-up circuit. If the user is using the bias-up circuit, this link must be inserted which will apply the 2.5 V reference voltage to the bias-up circuit. This causes a bipolar signal (applied to the bipolar vin input socket) to be biased up around +1.25 V before it is applied to the AD7492 VIN pin. - see also LK10 (below). When this link is in position "A" the bias-up circuit is supplied by the AD7492 internal reference. When this link is in position "B" the bias-up circuit is supplied by the AD780 external reference. If the bias up circuit is not being used this link should be removed. This link must be in position "A" if external power supplies are being used. In this position the control logic is being powered by the voltage applied to the VDD input. When power is being supplied from the EVAL-CONTROL BRD2, this link can be moved to position "B" if the user wants to drive the control logic from a separate +5 V which is generated on the EVAL-CONTROL BRD2. This link option selects the sleep mode that the AD7492 can be put into. When this link is in position "A" the part goes into full sleep when low power operation is selected. When this link is in position "B" the part goes into partial sleep when low power operation is selected. This link option selects the source of the CONVST input. When this link is in position "A" the CONVST input is provided by the EVAL-CONTROL BRD2. When this link is in position "B" the CONVST input is provided via the external socket, SK2. This link option selects the source of the RD input. When this link is in position "A" the RD input is provided by the EVAL-CONTROL BRD2. When this link is in position "B" the RD input is tied to GND. This link option selects the source of the CS input. When this link is in position "A" the CS input is provided by the EVAL-CONTROL BRD2. When this link is in position "B" the CS input is tied to GND. This link option sets the voltage applied to the VDRIVE pin on the AD7492. When this link is in position "A", VDRIVE is connected directly to the DVDD pin. When this link is in position "B", an external voltage must be applied to the VDRIVE pin Via J3. This link selects the source of the VDD supply. When this link is in position "A" VDD must be supplied from an external source via J2. When this link is in position "B" VDD is supplied from the EVAL-CONTROL BRD2. This link selects the source of the VSS supply. When this link is in position "A" VSS must be supplied from an external source via J2. When this link is in position "B" VSS is supplied from the EVAL-CONTROL BRD2. -2- LK2 LK3 LK4 LK5 LK6 LK7 LK8 LK9 REV. A EVAL-AD7492CB Continued on next page LK10 LK11 LK12 This link must be in position "A" if a bipolar AIN signal is being applied to the bipolar Vin socket, SK3. This link must be in position "B" if a unipolar AIN signal is being applied to the unipolar Vin socket, SK1. This link is used to connect in the impedence matching resistor, R5, for unipolar Vin. This link is used to connect in the impedence matching resistor, R7, for bipolar Vin. SET-UP CONDITIONS Care should be taken before applying power and signals to the evaluation board to ensure that all link positions are as per the required operating mode. Table I shows the position in which all the links are set when the evaluation board is sent out. All links are set for use with the EVAL-CONTROL BRD2. Table I. Initial Link and Switch Positions Link No. LK1 LK2 LK3 LK4 LK5 LK6 LK7 LK8 LK9 LK10 LK11 LK12 Position B B B A A A A B B A Inserted Inserted Function. Provides DC bias voltage to the analog bias-up circuit using AD780 external reference. The digital logic circuitry is powered from the EVAL-CONTROL BRD2. Part goes into partial sleep mode if low power operation selected. CONVST signal is provided by the EVAL-CONTROL BRD2 via J1. RD signal is provided by the EVAL-CONTROL BRD2 via J1. CS signal is provided by the EVAL-CONTROL BRD2 via J1. AD7492 VDRIVE pin is connected to the AD7492 DVDD pin. VDD is supplied by the EVAL-CONTROL BRD2 via J1. VSS is supplied by the EVAL-CONTROL BRD2 via J1. The AD7492 Vin pin is connected to the bipolar Vin. Unipolar Vin impedence matching resistor is connected into circuit. Bipolar Vin impedence matching resistor is connected into circuit. REV. A -3- EVAL-AD7492CB EVAL-CONTROL BRD2 INTERFACING Table II. 96-Way Connector Pin Functions. ROW A ROWB ROWC Interfacing to the EVAL-CONTROL BRD2 is via a 96-way connector, J1. The pinout for the J1 connector is shown in Figure 2 and its pin designations are given in Table II. 1 1 A B C 1 32 32 2 3 Figure 1. Pin Configuration for the 96-Way Connector, J1 D0 D1 DGND DGND D2 D3 D4 +5VD RD +5VD D5 D6 D7 DGND DGND D8 D9 D10 DGND FL0 DGND D11 DGND IRQ2 DGND CS +5VD DGND 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 96-Way Connector Pin Description D0-D11 +5VD Data Bit 0 to Data Bit 11. Three-state TTL outputs. D11 is the MSB. Digital +5 V supply. This can be used to provide a separate +5 V supply for the digital logic if required via LK2. Read. This is an active low logic input connected to the RD pin of the AD7492 via LK5. Chip Select. This is an active low logic input connected to the CS pin of the AD7492 via LK6. Flag zero. This logic input is connected to the CONVST input of the AD7492 via LK4. Interrupt Request 2. This is a logic output and is connected to the BUSY logic output on the AD7492. Digital Ground. These lines are connected to the digital ground plane on the evaluation board. It allows the user to provide the digital supply via the connector along with the other digital signals. Analog Ground. These lines are connected to the analog ground plane on the evaluation board. Negative Supply Voltage. This provides a negative supply to the on-board op-amps via LK9. Positive Supply Voltage. This provides a positive supply to the op-amps, the reference, the AD7492 and the digital logic. RD CS FL0 IRQ2 DGND DGND AGND AGND AGND AGND AGND AGND DGND AGND AGND AGND AGND AGND AGND AGND AGND DGND AGND AGND AGND AGND AGND AGND AGND AVSS AVDD AGND AVSS AVDD AGND AGND AVSS AVDD AGND AVSS AVDD When interfacing directly to the EVAL-CONTROL BRD2, all power supplies and control signals are generated by the EVAL-CONTROL BRD2. However, due to the nature of the DSP interface on the EVAL-CONTROL BRD2, AD7492 sampling rates greater than 750 KHz are not supported when interfacing the EVAL-AD7492CB directly to the EVALCONTROL BRD2. Note : The unused pins of the 96-way connector are not shown. -4- REV. A EVAL-AD7492CB SOCKETS OPERATING WITH THE EVAL-CONTROL BRD2 There are three input sockets relevant to the operation of the AD7492 on this evaluation board. The function of these sockets is outlined in Table III. Table III. Socket Functions Socket SK1 Function Sub-Miniature BNC Socket for unipolar analog input. Analog inputs in the acceptable AD7492 analog input range (0 V to REFIN) are applied to this socket. The signal is then buffered before it is applied to the AD7492 VIN pin. Sub-Miniature BNC Socket for external CONVST input. Sub-Miniature BNC Socket for Bipolar analog input The AD7492 can only accept analog inputs in the range 0 V to REFIN. Bipolar analog inputs in the range -1.25 V to +1.25 V applied to this socket are biased up to the acceptable AD7492 input range by the onboard bias-up circuit before being applied to the AD7492 VIN pin. The evaluation board can be operated in a stand-alone mode or operated in conjunction with the EVAL-CONTROL BRD2. This EVAL-CONTROL BRD2 is available from Analog Devices under the order entry "EVAL-CONTROL BRD2". When interfacing directly to this control board, all supplies and control signals to operate the AD7492 are provided by the EVAL-CONTROL BRD2 when it is run under control of the AD7492 software which is provided with the AD7492 evaluation board package. This EVAL-CONTROL BRD2 will also operate with all Analog Devices evaluation boards which end with the letters CB in their title. The 96-way connector on the EVAL-AD7492CB plugs directly into the 96-way connector on the EVAL-CONTROL BRD2. No power supplies are required in the system. The EVAL-CONTROL BRD2 generates all the required supplies for itself and the EVAL-AD7492CB. The EVALCONTROL BRD2 is powered from a 12 V AC transformer. Suitable transformers are available as an accessory from Analog Devices under the following part numbers: EVAL-110VAC-US: EVAL-220VAC-UK: EVAL-220VAC-EU: For use in the U.S. or Japan For use in the U.K. For use in Europe SK2 SK3 These transformers are also available for other suppliers including Digikey (U.S.) and Campbell Collins (U.K.). Connection between the EVAL-CONTROL BRD2 and the serial port of a PC is via a standard RS-232 cable which is provided as part the EVAL-CONTROL BRD2 package. Please refer to the manual which accompanies the EVALCONTROL BRD2 for more details on the EVAL-CONTROL BRD2 package. CONNECTORS There are three connectors on the AD7492 evaluation board as outlined in Table IV. Table IV. Connector Functions Connector J1 J2 J3 Function 96-Way Connector for EVAL-CONTROL BRD2 interface connections. External VDD, VSS & AGND power connector. External VDRIVE & DGND power connector. REV. A -5- EVAL-AD7492CB Figure 2. Main Screen SOFTWARE DESCRIPTION The software which controls the Evaluation Board Controller and hence the evaluation board has three main screens. The screen shown in Figure 2 shows the screen which appears when the software is run. The main function of this screen is to allow the user to read a predetermined number of samples from the evaluation board and display them in both the time and frequency domain. The screen can be divided into 3 sections. The upper third of the screen contains the control buttons, the menu bar and various status windows. The control buttons allow the user to enter the setup menu, take samples and get information about the software. The menu bar allows the user to select which printer port is to be used to control the Evaluation Board Controller, load and save data etc. The status windows indicate the setup of the evaluation board/device, number of samples taken and any information/error messages that are generated. The middle third of the screen is a Digital Storage Oscilloscope (DSO). When samples are uploaded from the Evaluation Board Controller they are displayed here. The samples can be displayed either as integer values or as voltages (determined by the input range of the device inquestion). Once samples have been displayed clicking at any point in the graph will display the sample number and value of the point directly beneath the cursor. Along the axis of the graph are the "zoom handles". These allow the user to zoom in and out to get a closer look at a particular sample if required. When another set of samples is taken the graph will attempt to display all values collected unless the Hold Zoom check box is ticked. In this case the graph will keep the same axis settings as for the previous set of data samples. Additional check boxes are provided to give the user control over the vertical and horizontal grids and data points. The lower third of the screen will show either a Fast Fourier Transform (FFT) of the data or a Histogram which shows the number of occurrances of each particular code read back. The FFT (the default option) is typically used when the user is concerned with examining an ADC's performance in the frequency domain while the Histogram will give an indication of the ADC's performance to DC signals. The option displayed can be toggled by clicking on the FFT Mode/Histogram Mode button in the top right of the screen. Figure 3 shows how the main screen looks when the Histogram Option is selected. -6- REV. A EVAL-AD7492CB Figure 3. Main Screen - Histogram Mode Setup Screen The Setup Screen is responsible for allowing the user to load a configuration file for the evaluation board. The configuration file will give the software detailed information about the evaluation board and part connected to the Evaluation Board Controller such as number of bits, maximum sampling rate, power supply requirements etc. The configuration file also tells the software the name of the DSP program file which it should download to the Evaluation Board Controller. These files are supplied by Analog Devices with the evaluation board. Figure 4 shows the Setup Screen. SETTING UP THE EVALUATION BOARD CONTROLLER been installed should be loaded before the printer port cable is connected between the Evaluation Board Con-troller and the PC. This will ensure that the printer port has been initialized properly. The printer port cable can then be connected between the PC and the Evaluation Board Controller. Running the Software The following text describes how the evaluation board Evaluation Board Controller and software should be set up for the user to begin using the complete system. The Evaluation Board Controller and evaluation board should be connected together (via the 96 way connector). The power should be applied to the Evaluation Board Controller. At this stage the red LED should be flashing which indicates that the Evaluation Board Controller is functional and ready to receive instructions. The software which should have REV. A With the hardware setup the user is now in a position to use the software to control the Evaluation Board Con-troller and evaluation board. In the software the user should select the File menu and click on Setup. This will display the setup form. A window on the left of the setup form list all the available configuration files. The con-figuration files are text based files which contain infor-mation about the particular evaluation board to be tested. The information will cover such things as the part name, number of samples to be taken, default and maximum sampling frequency power supply settings etc. The configuration file also contains the name of the DSP program file which is to be downloaded to the Evaluation Board Controller. The user should select the relevant configuration file and click Load. The Evaluation Board Controller will be reset and the DSP program will be downloaded. When the download has been completed the -7- EVAL-AD7492CB Figure 4. Setup Screen power supply settings indicated in the configuration file are set and the user may hear some of the relays clicking. The pull-down menus items such as number of samples and sampling frequency will have been set to the default values specified by the configuration file. The user is free to change these at will. Once all the settings had been decided the user can click Close to return to the main form. Taking Samples Load Raw Data: Selecting this option allows the user to load data which had been saved by the software during a previous session. Save Raw Data: Selecting this option allows the user to save the current set of sample data points. The data can be reloaded to the Evaluation Board Controller software at a later date or can be used by other programs for further analysis Save Binary Data: Selecting this option allows the user to save the current set of sample data points. The data is saved in binary format as a text file. This method can be useful for examining code flicker, looking for stuck bits etc. Save FFT Data: Selecting this option allows the user to save the current set of FFT data points. FFT data cannot be reloaded into the Evaluation Board Controller software but can be loaded into other software packages for further analysis. Exit: Quits the program. Printer Port: This menu item allows the user to select which printer port should be used for communication with the Evaluation Board Controller. LPT1: This option selects 0x378 as the printer port address. This is the default option. LPT2: This option selects 0x278 as the printer port address. PRN: This option selects 0x3BC as the printer port address. Help: This menu item gives information about the current revision of software for the particular evaluation board being used. When the user clicks Sample the software will instruct the Evaluation Board Controller to take the required number of samples at the required frequency from the evaluation board. These samples are then uploaded and displayed. An FFT and Histogram are also calculated and displayed. If the user clicks Cont Samp the software will repeat the process indefinitely until the user clicks the button again. While the software is continuously sampling data the other control buttons are disabled. Other Buttons The Reset button will cause the Evaluation Board Controller to perform a reset function. When this happens the power supplies are turned off and the program in DSP memory is lost. The user should repeat the setup instructions to download another program if required. The Quit button will exit the software, the program running on the Evaluation Board Controller is not terminated. MENU BAR ITEMS The main screen of the Evaluation Board Controller contains a number of options available as pull-down menu items. The functions of these are listed below. File Menu: Setup Menu: Selecting this option displays the Setup Screen as shown in Figure 4. -8- REV. A EVAL-AD7492CB SOFTWARE CONFIGURATION FILES Software Configuration Files give the Evaluation Board Controller software information on how the software and hardware should perform . They contain information such as the name of the DSP program to download, the default and maximum sample frequencies, the number of samples to take and the power supply settings to use. A typical Software Configuration File (*.cfg) is shown in Table V. Table V.: Typical Software Configuration File. [EVAL-CONTROL BOARD] partname:AD7492 programname:AD7492.PRG samplefrequency:100000 maxsamplefrequency:750000 samples:2048 +/-15V:on dvdd:5:on avdd:5:on bus:on ;options 2scomp, binary dataformat:binary numberofbits:12 inputVmax:2.5 inputVmin:0 [endofconfig] Figure 7. AD7492 Evaluation Board Circuit Diagram (ADC Section) REV. A -9- EVAL-AD7492CB Figure 5. AD7492 Evaluation Board Circuit Diagram -10- REV. A EVAL-AD7492CB Figure 6. AD7492 Evaluation Board Circuit Diagram REV. A -11- EVAL-AD7492CB Table VI. AD7492 Evaluation Board Bill Of Materials Qty. 1 2 1 1 1 1 1 10 2 13 5 1 1 1 6 2 1 1 2 2 2 3 1 1 1 1 1 8 Harwin 1 10 24 1 1 1 1 3 4 1 PartType AD7492BRU AD797BN OP07DP AD780AR MM74HC04M MM74HC08M SD103C Schottky Diode 10u., 10V (TAJ-B Series) 0.1u. 16V X7R (0603 size) 0.1u. 50V X7R (0805 size) 0.1u. 50V X7R (0805 size) 0.01u. 50V X7R (0805 size) 27p. 50V NPO (0603 size) 1n. 50V NPO (0805 size) 47u. 16V (TAJ-D Series) 22p. 100V NPO (0805 size) 4.7u. 16V (TAJ-B Series) 10 1% (0603 Size) 1K 1% (0805 Size) 100 1% (0805 Size) 51 1% (0805 Size) 20k 1% (0805 Size) 130 1% (0805 Size) 130 1% (0805 Size) 50K Multi-turn trimmer pot 220uH Inductor (8RHB Series) 2 pin header 4 (2+2) pin header 3 pin header (SIP3) Shorting Link Ultra Low Profile Sockets 96 Pin 90 DIN41612 Plug 3 Pin Terminal Block 2 Pin Terminal Block 40 Pin 90 IDC Ribbon Connector Gold 50 SMB Jack Stick-on .eet PCB RefDes U1 U2 U3 U4 U5 U6 U7 D1 C1 C3 C9 C11 C13 C15 C17 C19 C23 C29 C2 C4 C5 C7 C8 C10 C12 C14 C16 C18 C20-C22 C42 C38 C28 C30 C32 C34 C36 C24 C25 C27 C6 C31 C33 C35 C40 C39 C37 C26 C41 R1 R2 R3 R4 R8 R5 R7 R6 R9 R10 R11 R12 R13 L1 Order Number AD7492BRU AD797BN OP07DP AD780AR .EC 379-220 .EC 379-224 SD103C .EC 498-660 .EC 499-675 .EC 499-687 .EC 499-687 .EC 499-225 .EC 722-017 .EC 317-457 .EC 498-762 .EC-317-500 .EC 498-725 .EC 910-995 .EC 911-239 .EC 911-732 .EC 771-181 .EC 771-491 .EC 771-235 .EC 771-235 .EC 348-144 .EC 598-215 Supplier/Manuf ADI ADI ADI ADI Motorola Motorola AVX AVX AVX AVX AVX Philips AVX AVX AVX AVX Multicomp Multicomp Multicomp Multicomp Multicomp Multicomp Multicomp Bourns TOKO Harwin .EC 511-791 Harwin Berg Harwin Siemens Lumberg Lumberg 3M M/ACOM 3M LK1 .EC 511-705 LK2 LK4 LK5 LK6 LK7 LK8 LK9 LK10 LK3 LK1 - LK10 U3 U4 U5 J1 J2 J3 J4 SK1 SK2 SK3 Each Corner EVAL-AD7492CB .EC 671-927 .EC 528-456 .EC 519-959 .EC 269-931 .EC 151-786 .EC 151-785 .EC 727-714 .EC 310-682 .EC 148-922 n/a -12- REV. A EVAL-AD7492CB Figure 7. Component Side Artwork Figure 8. Solder Side Artwork REV. A -13- EVAL-AD7492CB Figure 6. Component Side Artwork -14- REV. A |
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