®
DEM-ADS1250
EVALUATION FIXTURE
FEATURES
DESCRIPTION
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The ADS1250U evaluation fixture provides an easy
and efficient method of evaluating the ADS1250U.
The evaluation fixture and PC software function as a
complete data acquisition system using a standard
parallel port. Data can be collected, analyzed, and
stored in either the time domain or frequency domain.
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EASY TO USE GRAPHICAL INTERFACE
Windows® 95 COMPATIBLE SOFTWARE
COLLECTS UP TO 32,768 CONVERSIONS
RETRIEVED DATA CAN BE VIEWED IN TIME
DOMAIN, FFT, OR AS INDIVIDUAL SAMPLES
HISTOGRAM FUNCTION DISPLAYS NOISE
DISTRIBUTION
AUTOMATICALLY CALCULATES STANDARD DEVIATION, MEAN, SNR, SINAD,
THD, AND SFDR
DATA CAN BE SAVED IN ASCII FORMAT
(EASILY IMPORTED INTO MICROSOFT®
EXCEL)
GRAPHS MAY BE PRINTED OR EMBEDDED INTO OTHER WINDOWS APPLICATIONS
The time domain analysis includes a histogram feature
which allows for verification of low noise and no
missing code performance. The frequency domain
analysis uses conventional FFT plots. The FFT analysis can also be modified with a user-selectable FFT
window. The time domain or frequency domain data
can be collected and displayed in either an on-demand
or periodic basis.
The design of the evaluation fixture’s hardware allows
the user to choose between several configurations,
including single-ended or differential mode input signals. An offboard reference voltage may also be applied to the device. Test points are included for all
digital signaling. In addition, a small prototyping area
is available on the analog board.
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111
Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
© 1999 Burr-Brown Corporation
SBAU002
LI-544
Printed in U.S.A. November, 1999
SYSTEM REQUIREMENTS
SETTING BOARD JUMPERS
Windows® 95
Standard Parallel Port
+5V DC Power Supply
±15V DC Power Supply (for single-ended to differential
signal converter)
• 6.2Mb free space on hard drive (maximum required)
• ADS1250 Demo Hardware
The analog board has several configuration jumpers. The
most important of these jumpers are the analog input selection jumpers (JMP1, JMP15, and JMP21-24). Direct connection allows both the positive and negative input of the
part to be provided by external sources (see Figure 1). To
connect directly to the inputs (J3 and J4), set the jumpers as
shown in Table I.
•
•
•
•
CONNECTING THE HARDWARE
The ADS1250 demonstration system contains two printed
circuit boards. The first board is the computer interface
board (A2702), which handles data buffering and parallel
port communication. The second is the analog board (PR277)
which contains the ADS1250 and all the support circuitry.
The computer interface board buffers the data from the
ADS1250 chip so that the data can be transferred to the
computer for analysis. The data link between the interface
board and the computer is comparatively slow, so the data is
first stored in buffer memory on the interface board and then
transferred to the computer. The Intel-compatible computer
connects to the interface board via the 25-pin cable. The
female end of the cable connects to J1 on the interface board.
The male end of the cable connects to the female parallel
port connector on the back of the computer.
The analog board connects to the interface board via a 36conductor ribbon cable. The cable is designed to lay flat in
between the boards. Do not twist the ribbon cable when
connecting the two boards (the connectors are not polarized). It does not matter which direction the ribbon cable
exits the connector.
Both boards must now be connected to a +5V DC supply
(the same unit can supply both boards). Connector P3 on the
interface board is the DC power input. Connector J1 on the
analog board is the other DC power input. Connector J5 on
the analog board is the DC power for the ±15V supply.
NOTE: Parallel ports are female 25-pin connectors, serial
ports are male 25-pin connectors. Do not connect to a serial
port.
Do not “daisy-chain” the interface board with any other
device. The demonstration board was designed to work on a
dedicated parallel port.
JUMPER
POSITION
JMP1
N/A
JMP15
2-3
JMP21
2-3
JMP22
2-3
JMP23
2-3
JMP24
2-3
TABLE I. Direct Differential Connection.
JMP1
1
ADS1250
JMP23
1
JMP21
1
JMP24
JMP15
1
J3
Negative
1
JMP22
J4
Positive
1
FIGURE 1. Jumper Settings for Direct Connection to Analog Inputs.
If the application requires a fixed common-mode voltage,
the board can be set to provide 2.5V DC common mode (see
Figure 2). The conversion circuitry is connected by the
jumper settings in Table II.
JUMPER
POSITION
JMP1
1-2
JMP15
1-2
JMP21
N/A
JMP22
1-2
JMP23
1-2
JMP24
1-2
TABLE II. Single-Ended Connection with 2.5V Common
Mode.
®
DEM-ADS1250
2
+5VDC
JMP1
1
1kΩ
5kΩ
5kΩ
1kΩ
JMP23
1
ADS1250
JMP21
1
JMP24
JMP15
1
1
JMP22
J4
Positive
1
NOTE: The supply connected to J4 (Positive Channel) must be floating (i.e., it must not share a ground connection with the power supply).
There is a gain of 2 associated with J4 (Positive Channel).
FIGURE 2. Jumper Settings for a Fixed Common-Mode Voltage to Analog Inputs.
The analog input can also be shorted directly to demonstrate
rms noise. To short the analog input, set the jumpers for
direct connection. Disconnect any sources at J3 and J4, and
connect jumper JMP17.
If the user wants to provide an arbitrary common-mode
signal, single-ended connection allows the input to be converted from two single-ended sources to a differential input
for the chip. J4 is the input for the signal, and J3 is the input
for the common-mode voltage (see Figure 3). The conversion circuitry is connected by the jumper settings in
Table III.
JUMPER
NOTE: Remember to remove the shorting jumper after the
test.
If an external reference is to be used, connect the reference
voltage to J2. To select the external reference voltage, set
JMP11 to position 2-3. To return to the internal voltage, set
JMP11 to position 1-2.
POSITION
JMP1
2-3
JMP15
1-2
JMP21
1-2
JMP22
1-2
JMP23
1-2
JMP24
1-2
There are several jumper locations on the board that do not
have header pins installed. These jumpers were included in
case the user wished to directly connect a logic analyzer or
apply external digital signals. For logic analyzers, a wire
may be soldered into one of the open pin holes. For external
digital signals, cut the copper trace on the board in between
the jumpers. Refer to Figure 15 for connections of the
jumpers.
TABLE III. Single-Ended Connection.
JMP1
1
1kΩ
JMP23
1
ADS1250
1kΩ
JMP21
1
JMP24
J3
Negative
JMP15
1
1
JMP22
1
J4
Positive
NOTE: The supply connected to J4 (Positive Channel) must be floating (i.e., it must not share a ground connection with the supply on J3).
There is a gain of 2 associated with J4 (Positive Channel).
FIGURE 3. Jumper Settings for a Single-Ended-to-Differential Voltage to Analog Inputs.
®
3
DEM-ADS1250
INSTALLING A PART IN THE SOCKET
INSTALLING THE SOFTWARE
The Robinson Nugent low profile socket on the analog
board has an ADS1250 installed as part of the kit. If the user
wants to change the part, use caution to properly orient the
part in the socket.
To install the software, first close all applications running on
the computer. If you do not close all applications, the install
may fail because a Windows system file could be in use.
Insert Disk 1 into the floppy disk drive. Click on the Start
button. Select RUN... and type A:setup in the dialog box
(assuming that A: is the drive that the disk is in). The setup
installation program will prompt for the installation directory (the default is recommended). The installation program
will prompt when the other disks in the set are needed.
The latching cover can be removed by using a small screwdriver or pair of tweezers to dislodge the mounting clips at
either end of the lead cover (remember to turn the power off
before attempting). The new part is placed with pin 1
(nearest the small dimple in the package) oriented to the
label “PIN 1” on the silkscreen (see Figure 4). There should
be no space between the part and pin 1 in the socket.
The setup program installs or updates all the necessary
Windows system DLLs and OCX controls. The actual program files are stored in C:\program files\demo1250. Setup
will also create an icon in the Start menu for the Demo1250
program.
If it is necessary to remove the Demo1250 software, open
the control panel and click on Add/Remove Programs. The
Demo1250 software will be listed as an option for uninstall.
COLLECTING DATA FOR THE FIRST TIME
Socket Base
Lead Cover
Start the software by selecting the Demo1250 icon from the
Start menu (Start/Programs/Demo1250). The program will
display an empty graph when it starts, as shown in Figure 5.
Correct Orientation
FIGURE 4. Device Orientation in Socket.
TROUBLESHOOTING
• If the red LED on the analog board is not lit, then +5V is
not being applied to the board.
• If either of the green LEDs on the interface board is not lit,
the Xilinx chips are not loaded properly. This may occur
if power is not applied or the socketed chips (U1, U2, U5
and U6) are not making a good connection.
• The Xilinx chips will fail to load (no green LEDs) if the
rise time of the +5V DC power supply is less than 25ms.
• There should not be a twist in the cable between the PC
interface board and the analog board.
• The cable for the parallel port does not require any type of
adapter to connect to the PC. The connector on the PC will
be a 25-pin female connector.
FIGURE 5. ADS1250 Demonstration Software Screen.
• If the supply wires are accidentally connected backwards,
correct the problem and then wait approximately 20 seconds before applying power. The supply lines have
resettable fuses which must cool down before they will
reset.
The next step is to set the program for the correct parallel
port. Click on the menu titled “Settings” and an options
dialog box will appear. Click on the tab labeled “Computer”.
Press the button labeled “Run Autodetect” and the program
will display the parallel ports detected on the computer.
®
DEM-ADS1250
4
Set the combo box for the port address of the parallel port the
interface board is connected to. Click on “OK” (see
Figure 6).
SETTING HARDWARE OPTIONS FOR THE ADS1250
FIGURE 6. Parallel-Port Detection Screen.
FIGURE 8. Hardware Configuration Screen.
The option dialog will disappear and the empty graph will
display again. To retrieve data from the board, click on the
menu icon that looks like a camera (or press CTRL-D). If
everything is working correctly, the status bar at the bottom
of the window will count up and a time domain graph of the
collected data will appear on the screen, as shown in
Figure 7.
The “Hardware” tab of the options dialog box will allow
changes to the following parameters:
Clicking on the menu option “Settings” will open up the
options dialog box shown in Figure 8.
Gain Range: Click on the radio button for the gain setting
that is to be used.
Output Format: This option controls the display of the data
on the time domain graph. Unchanged integer is the data
directly from the chip. Full-Scale Normalized to 1 adjusts
the data so that full-scale range is ±1 (the data from the chip
is scaled). Voltage adjusts the data so that the display is in
volts (assuming a 4.1V reference).
Chip Select: By default, chip select is only active when
communication with the chip occurs. Setting this option
forces chip select to be active all the time.
Serial Clock: It is only necessary to pulse the data clock
when data is being shifted out of the chip. Setting this option
forces the data clock to be on all the time.
Serial Synchronization: Communication with the chip is
normally synchronized to the rising edge of the main clock.
Setting this option forces the data to synchronize with the
falling edge of the clock.
Read-Back Delay: This option adds a delay time between
chip select asserted low and serial clock pulses. The number
displayed represents the number of clock cycles.
FIGURE 7. Data Retrieval Screen.
Serial Frequency: This option reduces the clock frequency
of the serial clock. The default clock frequency is fs/2, where
fs is the main clock frequency.
To adjust the number of samples retrieved from the board,
move the slider at the bottom of the window or insert the
desired number into the numerical display. For detailed
software instructions, read the section titled “Exploring
Retrieved Data.”
Oscillator Frequency: This adjusts software delays and the
FFT plot, if the user replaces the oscillator on the interface
board with another frequency. The oscillator frequency is
not changed by this option; it is simply used to display
information in the proper format.
If the graph did not display or if a flat line is displayed,
recheck all the cable connections for data and power to the
two demo boards.
®
5
DEM-ADS1250
EXPLORING RETRIEVED DATA
In order to activate any of the changes, the button “OK” or
“Apply” must be pressed after the changes are made. If the
button “Cancel” is pressed or the window is closed, no
changes will be made.
Retrieving Data
There are two methods for data retrieval: single capture and
continuous read. For single capture, press the toolbar button
that looks like a camera, or type CTRL-D. This will trigger
a single read cycle.
NOTE: The ADS1250 does not support “Chip select always
low” and “Serial clock always on” at the same time.
Continuous read mode will trigger a new read cycle 0.5
seconds after the previous cycle is done. To activate continuous read, press the toolbar button that looks like a stopwatch,
or type CRTL-R. To deactivate continuous read, simply
repeat the command.
SETTING FFT OPTIONS FOR THE ADS1250
Clicking on the menu option “Settings” and selecting the
“FFT” tab will open up the options dialog box shown in
Figure 9.
At the bottom of the main window is a scroll bar and text
box. This is the control for the number of samples collected.
Slide the bar or input a new number in the box to change the
number of samples. The maximum number of samples that
can be collected is 32,768.
Viewing Data
Data can be viewed on screen four different ways: as a time
domain plot, a Fast Fourier Transform, a hexadecimal table,
or as a histogram. To select the different views, choose from
among the four buttons on the toolbar or select from the
View menu.
FIGURE 10. Toolbar.
FIGURE 9. FFT Configuration Screen.
Graph Options
The “FFT” tab of the options dialog box will allow changes
to the following parameters:
All the selections for changing the display of the graphs are
accessed by right-clicking on the graph itself. This will
display a small pop-up list of options as shown in
Figure 11.
FFT Window: This group of radio buttons allows selection
of different windows for the FFT data. For evaluations of a
low noise part like the ADS1250, sophisticated windows
like Continuous 5th Derivative and Blackman-Harris are
recommended.
Calculations: The calculations for the SNR, THD, SFDR,
and SINAD are based on the number of FFT bins shown. If
a different resolution is required, the number of bins used
can be changed here.
Display: For further insight into the FFT calculations, the
checkboxes in this section will display markers on the FFT
plot which define the bin boundaries used.
In order to activate any of the changes, the button “OK” or
“Apply” must be pressed after the changes are made. If the
button “Cancel” is pressed or the window is closed, no
changes will be made.
FIGURE 11. Graphic Options Pull-Down Menu.
®
DEM-ADS1250
6
Viewing Style selects color or black and white display. Font
Size changes the size of the titles and labels on the graph.
Numeric Precision changes the number of significant digits
after the decimal point. Plotting Method allows the selection
of different plot types (e.g., line, bar, point, etc.). Data
Shadows displays a dark background behind the data in
some plotting methods. Grid Lines controls the display of
the X and Y axis grid lines. Grid In Front is used to force the
display of the grid. Include Data Labels will display the X
and Y coordinates of every point on the graph. Mark Data
Points will place a marker at each data point for easy
viewing.
The export dialog allows the user to choose between a
Windows MetaFile (for embedding into another application), a bitmap (a exact replica of what is displayed on the
screen), and text. The user can also export to the clipboard,
a file, or the printer.
Saving Data
Aside from exporting data from the graphs, it is possible to
save the collected data directly to a text file. Choosing Save
from the File menu will save data to a comma-delimited text
file that is compatible with Microsoft Excel (.csv).
The data which is saved depends on the active plot. If the
time domain plot is visible, the time domain points will be
saved to the disk. If the FFT plot is visible, then the
individual points of the FFT will be saved.
The time domain data is saved in a single column as shown
in Figure 13. The FFT data is also saved in a single column
as shown in Figure 14.
To have the graph fill the entire screen, select the Maximize
option. This option is useful as a print preview of the graph.
To add annotation to the graph, such as custom titles, select
the Customization Dialog option. This will open a dialog
screen which will allow edits of titles and labels.
Zooming
To zoom in on any section of the time domain graph, simply
left-click and drag over the area of interest. A shaded box
will appear when dragging over the area. To undo the zoom,
right-click to display the pop-up menu and choose the option
for Undo Zoom.
The FFT graph will only zoom on the X axis.
Printing
Printing may be started by pressing the printer icon, or by
selecting Print from the File menu. A small dialog box will
appear and allow printer selection and setup. Page setup may
also be accessed through the File menu.
The print function only prints the current graph. The hexadecimal table will not print.
Exporting Data
To export data to other applications, right-click on the
current graph and choose the option for export dialog shown
in Figure 12.
FIGURE 13. ADS1250 Data File Time Domain Samples.
FIGURE 12. Export Dialog Screen.
FIGURE 14. ADS1250 Data File FFT Samples.
®
7
DEM-ADS1250
PARTS LIST
PC INTERFACE BOARD (A2702)
PART LOCATION
# PER KIT
PART NUMBER
VENDOR
U1, U2
2
XC3142A-3PC84C
Xilinx
Programmable Gate Array
U1, U2 (sockets)
2
PCS-084A-1
Augat
84-Pin PLCC Socket
C8, C10
2
503AHL
Rogers
U5, U6
2
AT17C65
Xilinx
Gate Array Control Prom
U5, U6 (sockets)
2
508-AG11D-E-S
Augat
8-Pin Single Wide DIP Socket
U8, U9, U10
3
IDT71256SA15TP
IDT
U12
1
74HCT244N
TI
U3, U4, U11
3
74HCT541N
TI
J1
1
747842-6
AMP
J2
1
3431-1202
3M
LED1, LED2
2
CMD5453
Chicago Miniature
U7
1
US-685-96
US Crystal
RN1, RN2
2
CSC10A-01-103F
Dale
10-Pin SIP Resistor Network (10kΩ, 9R, 1C)
R1-R4, R6-R14, R16
14
RN55C4751F
Dale
4.7kΩ Resistor, 1%
R5, R15
2
RN55C1001F
Dale
1kΩ Resistor, 1%
R22-R25
4
RN55C1002F
Dale
10kΩ Resistor, 1%
D1
1
1N5820
Motorola
C2-C7, C9, C11, C13, C14
10
C320C104K1R5CA
Kemet
C1
1
T110B106K020AS
Kemet
P3
1
2SV-02
Augat/RDI
Stand-Offs
8
313-6487-016
E.F. Johnson
Screws
8
F1
1
Decoupling Capacitors for Xilinx
8x32K Static RAM
Digital Buffers
Digital Buffers
25-Pin Male Right-Angle D Connector
34-Pin Male Ribbon Connector
LED (2V, 20mA)
9.6MHz Clock Oscillator
1W Diode
0.1µF Capacitors
10µF Tantalum Capacitor, 20V, 10%
Terminal Block
1/2" Hex Spacer, 6-32
1/4" Round Head Screw, 6-32
RUE090
Raychem
®
DEM-ADS1250
DESCRIPTION
8
PolySwitch Resettable Fuse
PARTS LIST (Cont.)
DUT BOARD (PR277)
PART LOCATION
# PER KIT
PART NUMBER
VENDOR
13
T491C106K020AS
Kemet
10µF, 20V Tantalum Capacitor
13
C1206C104K5RAC
Kemet
0.1µF, 50V Ceramic Capacitor
Kemet
0.1µF, 100V Ceramic Capacitor
0.01µF, 50V Ceramic Capacitor
C1, C4, C9, C11, C13, C18, C20,
DESCRIPTION
C22, C23, C25, C27, C28, C29
C2, C5, C10, C12, C14, C17, C19,
C21, C24, C26, C30, C31, C32
C3, C7
0
C6
1
C322C104K1R5CA
Not Installed
C8
1
C1206C103K5RAC
Kemet
D1
1
LM4040AIZ-4.1
National
D2, D4, D5
1
1N5821
Motorola
D3
1
HLMP-3201
HP
DUT1
1
SOP-20B-SMT-TT
Robinson Nugent
F1-F3
3
RUE090
Raychem
J1
1
ED1930
On-Shore Tech
J2-J4
3
227161-2
AMP
J5
1
ED1931
On-Shore Tech
JMP1, JMP11, JMP15,
7
TSW-103-07-T-S
Samtec
3-Pin Header, 100mil
JMP17
1
TSW-102-07-T-S
Samtec
2-Pin Header, 100mil
P1
1
3431-1202
3M
R1-R2
2
CRCW12061001F
Dale
1kΩ Resistor, 0.1%
R15
1
RN55C4991B
Dale
4.99kΩ Resistor, 0.1%
R16
1
RN55C1002F
Dale
10kΩ Resistor, 1%
R18
1
CRCW12065620F
Dale
562Ω Resistor, 1%
R19-R27
9
CRCW12061000F
Dale
100Ω Resistor, 1%
R28
1
CRCW120610R0F
Dale
10Ω Resistor, 1%
Dale
10Ω Resistor, 1%
4.99kΩ Resistor, 1%
Voltage Reference, 4.1V
1W Diode
LED (2V, 20mA)
20-Pin SOIC socket
PolySwitch Resettable Fuse
Terminal Block, 2 Position
Right-Angle BNC Connector
Terminal Block, 3 Position
JMP21-JMP24
R29
1
RN55C10R0B
R3-R4
2
FRJ-55
R9, R12
2
CRCW12064991F
Dale
34-Pin Male Ribbon Connector
0Ω Resistor
Screws
4
Stand-offs
4
313-6487-016
E.F. Johnson
1/4" Round Head Screw, 6-32
1/2" Hex Spacer, 6-32
U1, U4
2
OPA350U
Burr-Brown
Single-Supply Op Amp
U2
1
74HCT244N
TI
U3
1
74HCT541N
TI
U5, U6
2
OPA627BP
Burr-Brown
10
50863-5
AMP
8
SNT-100-BK-T
Samtec
Jumper Block
PART NUMBER
VENDOR
DESCRIPTION
Digital Buffers
Digital Buffers
Bipolar Op Amp
Pin Sockets
CABLES
PART LOCATION
# PER KIT
Parallel Port
6 Feet
AC25G
AMP
Parallel Port
1
CMM25G
CW Industries
25-Pin D-Sub Male Connector
25-Conductor Ribbon Cable
Parallel Port
1
CFM25G
CW Industries
25-Pin D-Sub Female Connector
PC Interface to DUT Board
2
3414-6034
3M
PC Interface to DUT Board
6 Inches
AC34G
AMP
34-Pin Wiremount Socket
34-Conductor Ribbon Cable
®
9
DEM-ADS1250
FIGURE 15a. Schematic for Device Board (PR277).
®
DEM-ADS1250
10
FIGURE 15b. Schematic for Device Board (PR277).
®
11
DEM-ADS1250
FIGURE 16a. Schematic for PC Interface Board (A2702).
®
DEM-ADS1250
12
FIGURE 16b. Schematic for PC Interface Board (A2702).
®
13
DEM-ADS1250
®
DEM-ADS1250
14
FIGURE 17. Layout of Device Board, Top Side (PR277).
15
DEM-ADS1250
®
FIGURE 18. Layout of Device Board, Bottom Side (PR277).
®
DEM-ADS1250
16
FIGURE 19. Layout of PC Interface Board, Top Side (A2702).
17
DEM-ADS1250
®
FIGURE 20. Layout of PC Interface Board, Bottom Side (A2702).
IMPORTANT NOTICE
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accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.
Customers are responsible for their applications using TI components.
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Copyright  2000, Texas Instruments Incorporated