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FEATURES Full-Featured Evaluation Board for the AD7475/95 EVALUATION-BOARD CONTROLLER Compatible Stand Alone Capability On-Board Analog Buffering and Reference Various Linking Options PC Software for Control and Data Analysis when used with EVALUATION-BOARD CONTROLLER Patchwork Area for User Expansion INTRODUCTION
Evaluation Board for 1MSPS, 12-Bit ADC
EVAL-AD7475/AD7495CB
OPERATING THE AD7475/AD7495 EVALUATION BOARD Power Supplies
When using this evaluation board with the EVALUATION-BOARD CONTROLLER all supplies are provided from the EVALUATION-BOARD CONTROLLER through the 96 way connector. When using the board as a stand alone unit external supplies must be provided. This evaluation board has six power supply inputs: VDD, AGND, +12V, -12V, AGND, and DGND. If the evaluation board is used in stand-alone mode +5V must be connected to the VDD input to supply the AD7475/AD7495 VDD pin and the AD780 voltage reference. +12V and -12V are used to supply the op-amps. The VDRIVE pin can be driven by a voltage between +3V and +5V allowing the evaluation board to be connected to both +3V and +5V systems. The supplies are decoupled to the relevant ground plane with 10F tantalum and 0.1F multilayer ceramic capacitors at the point where they enter the board. The supply pins of all the op-amps and reference are also decoupled to AGND with 10F tantalum and a 0.1F ceramic capacitor. The AD7475/AD7495 AVDD supply pin is decoupled to AGND with 10 F tantalum and 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 AD7475/AD7495.
This Technical Note describes the evaluation board for the AD7475/AD7495 which is a fast 12-bit high speed, low power successive-approximation ADCs. The parts operate from a sinlge 2.7 V to 5.25 V power supply and feature throughput rates up to 1 MSPS. Full data on the AD7475/AD7495 is available in the AD7475/AD7495 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 +2.5V or +3V ultra high precision bandgap reference and an AD711 op-amp used to buffer the analog input. There are various link options which are explained in detail on page 2. Interfacing to this board is through a 96-way connector. This 96-way connector is compatible with the EVALUATION-BOARD CONTROLLER which is also available from Analog Devices. External sockets are provided for the REFIN input and the VIN input.
FUNCTIONAL BLOCK DIAGRAM
ANALOG INPUT Vdd AD7475/A D7495
CS
SDATA SCLK EXTERNAL REFERENCE Vdrive
BIAS UP CIRCUIT
Vdd
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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
EVAL-AD7475/AD7495CB
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 connect the input of the AD711 op-amp to ground if the user needs to do this. When this link is in position "A" a signal applied to the AIN socket is routed to the input of the AD711 opamp. This is the normal application for this link. When this link is in position "B", the input of the AD711 op-amp is tied to GND. This link option controls the program pin of the AD780 voltage reference. When this link is "inserted" the AD780 output is set to +3.0 V. When this link is "removed" the AD780 output is set to +2.5 V This link is used to select the source of the reference voltage applied to the AD7475 REFIN pin. When this link is in position "A", the AD780 provides the 2.5V reference to the AD7475. When this link is in position "B" an external reference must be supplied to the AD7475 via J5. For the AD7495 this pin must be removed This link selects the source of the VDD +5V supply. When this link is in position "A" the +5V is supplied from an exteranl source via J6. When this link is in position "B" the +5V must be supplied from the EVALUATION-BOARD CONTROLLER This link option selects the source of the VDRIVE input. When this link is in position "A" the VDRIVE supply voltage is provided from VDD. When this link is in position "B" the VDRIVE supply voltage is provided from the EVALUATION-BOARD CONTROLLER. When this link is in position "C" an external VDRIVE supply voltage must be supplied via J7. This link option is used to select the source of the +12V supply In position A, the +12V is supplied from the EVALUATION-BOARD CONTROLLER through the 96 way connector. In position B, the +12V is supplied from an external source through the power connector, J8. This link option is used to select the source of the -12V supply. In position A, the -12V is supplied from the EVALUATION-BOARD CONTROLLER through the 96 way connector. In position B, the -12V is supplied from an external source through the power connector, J8. This link option sets the dc bias voltage applied to the optional bais-up/filter circuit. When the link is in position "A", the bias voltage is set to the same level as the voltage that is applied to the REF IN on the AD7475 and the REF OUT pin on the AD7495. In this configuration a bipolar anlag input applied to the Vin SMB socket as a unipolar signal biased around Vref/2. When in position "B", the bias voltage is set to AGND. In this configuration the bias up circuit is not used. This link option adds a 50 Ohm termination to AGND at the Ain socket. In most applications this link will be left unconnected. If a 50 Ohm termination is required, this link should be inserted. This link option adds a 50 Ohm termination to AGND at the Vin socket. In most applications this link will be left unconnected. If a 50 Ohm termination is required, this link should be inserted. When both these links are in position "A", for slower SCLK frequencies, giving valid data on the rising edge. When both these links are in position "B", for fast SCLK frequencies, giving valid data on the falling edge, the SCLK signal is connected directly to the AD7898 SCLK pin. This is the normal position for these 2 link options.
LK2
LK3
LK4
LK5
LK6
LK7
LK8
LK9 LK10 LK11, LK12
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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.
Table I. Initial Link and Switch Positions
Link No. LK1 LK2 LK3
Position A removed A removed
Function. Ain is tied to the input of the AD711 buffer op-amp. AD780 is set to provide a + 2.5 V reference. The on-board AD780 voltage reference supplies the REFIN pin of the AD7475. The internal + 2.5V reference on the AD7495 is used on the AD7495 control board V DD (+5V) supplied by the EVALUATION-BOARD CONTROLLER via J5. VDRIVE pin of the AD7475/AD7495 is connected to VDD (+5V) +12V supplied from EVAL-CONTROL BOARD via J5. -12V supplied from EVAL-CONTROL BOARD via J5. Vref is chosen as the dc bias voltage for the bias-up circuit. 50 Ohm termination is not selected. 50 Ohm termination is not selected. SCLK signal from EVALUATION-BOARD CONTROLLER is not inverted, (for faster values of SCLK).
LK4 LK5 LK6 LK7 LK8 LK9 LK10 LK11, LK12
B A A A A removed removed B
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EVAL-AD7475/AD7495CB
EVALUATION BOARD INTERFACING
Interfacing to the evaluation board is via a 96-way connector, J1. J1 is used to connect the evaluation board to the EVAL-CONTROL BOARD or other system. The pinout for the J5 connector is shown in Figure 1 and its pin designations are given in Table II.
Table II. 96-Way Connector Pin Functions.
1 A B C 1
32
ROW A
ROWB
ROWC
1
32
2 3 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 AVDD AVDD AVDD AGND -12V DGND AGND AGND AGND AGND AGND AGND DGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND +12V DGND AGND AGND AGND AGND AGND AGND DGND DGND DGND DGND DGND DGND DGND TFS0 SCLK0 DGND DGND DR0 RFSO SCLK0
Figure 1. Pin Configuration for the 96-Way Connector, J5
96-Way Connector Pin Description
DR0
DATA RECEIVE ONE: Serial Data from the AD7898 is provided at this output. Sixteen bits of data are provided with four leading zeroes followed by twelve bits of conversion data which is provided MSB first. SERIAL CLOCK ZERO: This continuous clock is connected to the SCLK pin of the AD7898 via LK7 to obtain serial data from the AD7898. TRNSMIT FRAME SYNC ZERO, RECEIVE FRAME SYNC ZERO: Both of these inputs are conncected to the AD7898 CS/ CONVST pin via LK5 to initiate conversions and to frame the serial data tansfer. 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. Analog +5V Supply. These lines are connected to the AVDD supply line on the board via LK4. +12V Supply. This line is connected to the +12V supply line on the board via LK8. -12V Supply. This line is connected to the -12V supply line on the board via LK9.
SCLK0
TFS0 RFS0
DGND
AGND
AVDD +12V -12V
Note : The unused pins of the 96-way connector are not shown.
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CONNECTORS
There are nine input/output connectors relevant to the operation of the AD7475/AD7495 on this evaluation board. The function of these connectors is outlined in Table III.
Table III. Connector Functions
OPERATING WITH THE EVAL-BOARD CONTROLLER
Connector J1 J2 J3 J4 J5 J6 J7 J8
Function Sub-Miniature BNC socket for Ain input. Sub-Miniature BNC socket for Ext Vref input. Sub-Miniature BNC socket for Vin input. Sub-Miniature BNC socket for Vbiased output. 96-Way Connector for Serial Interface & Power Supply connections. External VDD & GND power connector. External VDRIVE & GND input power connector. External +12V, -12V & AGND power connector
The evaluation board can be operated in a stand-alone mode or operated in conjunction with the EVALUATION-BOARD CONTROLLER. This EVALUATIONBOARD CONTROLLER is available from Analog Devices under the order entry "EVAL-CONTROL BRD2". When operated with this control board, all supplies and control signals to operate the AD7898 are provided by the EVALUATION-BOARD CONTROLLER when it is run under control of the AD7475/AD7495 software which is provided with the AD7475/AD7495 evaluation board package . This EVALUATION-BOARD CONTROLLER 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-AD7475/AD7495CB plugs directly into the 96-way connector on the EVALUATION-CONTROL BOARD. No power supplies are required in the system. The EVALUATION-BOARD CONTROLLER generates all the required supplies for itself and the EVAL-AD7475/AD7495CB. The EVALUATION-BOARD CONTROLLER is powered from a 12V ac transformer. This is a standard 12V ac transformer capable of supplying 1A current and is 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
These transformers are also available for other suppliers including Digikey (U.S.) and Campbell Collins (U.K.). Connection between the EVALUATION-BOARD CONTROLLER and the serial port of a PC is via a standard RS-232 cable which is provided as part the EVALUATION-BOARD CONTROLLER package. Please refer to the manual which accompanies the EVALUATIONBOARD CONTROLER for more details on the EVALUATION-BOARD CONTROLLER package.
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EVAL-AD7475/AD7495CB
Figure 2. AD7475/AD7495 Main Screen - FFT Mode
SOFTWARE DESCRIPTION
Included in the EVAL-AD7475/AD7495CB evaluation board package is a CD ROM which contains software for controlling and evaluating the performance of the AD7475/AD7495 when it is operated with the EVALUATION-BOARD CONTROLLER. When the CD is inserted into the PC an installation program will automatically begin. This program will install the evaluation software onto the users machine and will also install the technical Note for the AD7475/AD7495 evaluation board as well as the datasheet for the AD7475/AD7495. All literature on the CD is in Adobe's Portable Documation format (PDF) and will require Acrobat ReaderTM to be viewed or printed. The user interface on the PC is a dedicated program written especially for the AD7475/AD7495. The software which controls the Evaluation Board Controller and hence the AD7475/AD7495 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 the 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 most section of the screen contains the control buttons, the menu bar and the status windows.The controll buttons allow the user to enter the set-up menu, take samples, and get information about the software. There are also power down/up options in the control buttons. These buttons allow the user to place the part into power down, and power the part up again. There are two powerdown modes associated with the AD7475/AD7495, partial powerdown and full powerdown. To enter partial power down the ' PowerDown ' button should be pressed once. To enter Full power down the ' PowerDown ' button should be pressed twice( see modes of operating section of the AD7475/AD7495 datasheet ). 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 window indicates the set up of the AD7475/AD7495 evaluation board, the number of samples taken and any information messages that are generated. The middle section of the AD7475/AD7495 Main 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 as either interger values or as voltages . Once the samples are displayed clicking any point on the graph will display the sample number and the 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 are taken the graph will attempt to display all values collected unless the Hold Zoom check box is ticked. If the Hold zoom box is ticked the graph will keep the same axis settings as for the previous set of data samples. There are additional check boxes in this section to give the user control over the vertical and horizontal grids and data points. The lowest section of the screen will show either a Fast Fourier Transform (FFT) of the data, or a histogram, which shows the number of occurances of each particular code read back. The FFT ( default option ) is typically used when the user is concerned with examining the AD7475/AD7495's performance in the frequency domain, while the Histogram will give an indication of the AD7475/AD7495's performance to dc signals. The option displayed can be changed by clicking on the FFT Mode/Histogram Mode button in the top right of the screen. Figure 3 shows how the Main Screen would look if the Histogram Mode was selected. -6- REV. 0
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Figure 3 AD7898 Main Screen - Histogram Mode
Setup Screen
The Setup Screen is responsible for allowing the user to load the AD7475/AD7495 configuration file for the evaluation board. The configuration file will give the software detailed information about the AD7475/AD7495 evaluation board and part connected to the Evaluation Board Controller such as number of bits, maximum sampling rate, power supply requirements etc. The AD7475/AD7495 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 CONTROLLER THE EVALUATION BOARD
connected between the PC and the Evaluation Board Controller.
Running the AD7475/AD7495 Software
The following text describes how the evaluation board Evaluation Board Controller and how AD7475/AD7495 software should be set up for the user to begin using the complete system. The Evaluation Board Controller and AD7475/AD7495 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 AD7475/AD7495 software which should have been installed should be loaded before the printer port cable is connected between the Evaluation Board Controller and the PC. This will ensure that the printer port has been initialized properly. The printer port cable can then be
With the hardware setup the user is now in a position to use the software to control the Evaluation Board Controller 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 configuration files are text based files which contain information about the particular evaluation board to be tested - AD7475/AD7495.cfg. 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 AD7475.cfg configuration file and click Load. The AD7475.cfg file will work for both the AD7475 and the AD7495. The Evaluation Board Controller will be reset and the DSP program will be downloaded. When the download has been completed the 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.
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Figure 4. The Setup Screen
Taking Samples
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
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.
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.
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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 Listing 1.
[EVAL-CONTROL BOARD] partname:AD7475 programname:ad7475.PRG samplefrequency:100000 maxsamplefrequency:1000000 samples:2048
+/-15V:on dvdd:5:on avdd:5:on bus:on ;options 2scomp, binary dataformat:binary numberofbits:12 inputVmax:2.5 inputVmin:0
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Figure 4. AD7475/95 Evaluation Board Circuit Diagram
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Qty 14 Reference Designator C1 C4 C5 C10 C11 C13 C16 C19 C21 C23 C25 C26 C28 C33 C2 C3 C6 C9 C12 C14 C15 C17 C18 C20 C22 C24 C27 C29 C32 C7 C8 C8 C30 C31 R1 R2 R3 R4 R6 R5 R7 R8 D1 U1 U2 U3 U4 U5 J1 J2 J3 J4 J5 J6 J7 J8 LK1 LK3 LK4 LK6-LK8 LK11 LK12 LK2 LK9 LK10 LK5 T1 T2 T3 U1 U2 U3 U5 Each corner EVAL-AD7495CB Description/Value 10uF 35V Tant. Manuf. No. TAP10K35CCSY Supplier No. FEC 664-881
15
0.1uF Ceramic 50 V
MCDR25104X7RK0050
FEC 750-920
1 1 1 2 5 1 2 1 1 1 1 1 1 3 1 2 1 8 3 1 3 2 4 1
0.01uF Ceramic 50 V 0.22uF Ceramic 50 V 0.1uF Ceramic 50 V 68pF Ceramic 1K 0.25W 0.1% RC55 3K 0.25W 0.1% RC55 51W 0.25W 1% SD103C Schottky Diode AD711KN Op-Amp AD780AN Voltage Reference ADOP467G AD7495AR 74LS04N
MCDR25103X7RK0050 MCDR50224X7RK0050 MCDR50104X7RK0050 MR051A680JT0001 Welwyn Welwyn Multicomp DO35 ADI AD711KN ADI AD780AN ADI ADOP467G SO8NB DM74LS04N
FEC 750-890 FEC 750-967 FEC 750-955 FEC 669-714 FEC 339-179 FEC 339-635 FEC 543-070
ADI ADI ADI ADI FEC 373-450 FEC 310-682 FEC 104-986 FEC 151-785 FEC 151-786 FEC 511-791 FEC 511-705 FEC 511-780 FEC 240-333 FEC 519-959 FEC 651-813
50W Gold Plated PCB SMB Jack M/ACOM DIN41612 C96 900 plug 2 Pin Power Connector 3 PIN Power Connector 2x2 Way Jumper 2 Way Jumper 2x3 way jumper Black Testpoint Ultra low profile socket strip Stick on feet P.C.B.
Figure 4. AD7475/95CB Bill of Materials
Siemens Lumberg KRM2 Lumberg KRM3 Harwin Harwin Harwin W Huges Harwin 3M
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Figure 5. Component Side Artwork
Figure 6. Solder Side Artwork
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Figure 7. AD7475/AD7495 Evaluation Board Component Placement Drawing.
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