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a
Evaluation Board 400kSPS, 14-Bit ADC
FEATURES
Full-Featured Evaluation Board for the AD7899
Eval-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 Eval-Board Controller
INTRODUCTION
This Technical Note describes the evaluation board for the
AD7899 high speed, low power, 14-bit A/D converter that
operates from a single 5 V supply. Full data on the AD7899
is available in the AD7899 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 +2.5V
ultra high precision bandgap reference and an op-amp for the
analog inputs. 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 EVAL-BOARD
CONTROLLER which is also available from Analog Devices. External sockets are provided for the optional, external, CONVST and CLKIN and V
inputs and the
DRIVE
VIN1-VIN4 inputs.
EVAL-AD7899CB
OPERATING THE AD7899 EVALUATION BOARD
Power Supplies
When using this evaluation board with the EVAL-BOARD
CONTROLLER all supplies are provided from the EVALBOARD CONTROLLER through the 96 way connector.
When using the board as a stand alone unit external supplies
must be provided. This evaluation board has seven power
supply inputs: V
D
. If the evaluation board is used in stand-alone mode
GND
+5V must be connected to the V
AD7899 V
pin and the AD780 voltage reference. +12V and
DD
-12V are used to supply the op-amps. The V
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 10µF tantalum and 0.1µF 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
A
with 10µF tantalum and a 0.1µF ceramic capacitor. The
GND
AD7899 AV
DD
tantalum and 0.1µF 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, A
location close to the AD7899.
, A
DD
supply pin is decoupled to A
GND
, +12V, -12V, A
GND
and D
GND
GND
input to supply the
DD
DRIVE
GND
. These are connected at one
, V
DRIVE
and
pin can be
with 47uF
Fig. 1: FUNCTIONAL BLOCK DIAGRAM
ANALOG
INP UT
ANALOG
SIGNAL
CONDITIONING
EXTERNAL
REFERENCE
AD7899
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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.
OR
RS
FE
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BU
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TA
GI
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One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
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96
EV AL-AD7899CB
Link and Switch Options
There are 9 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 option selects the input range of the ADC. The position of this link is determined by the input
range required by the user. Please refer to the AD7899 data sheet for more information.
When this link is in position "A" V
When this link is in position "B" V
LK2 This link selects the reference source for the AD7899.
When a link is in position "A" the AD780 is selected as the reference source.
When a link is in position "B" an external voltage applied to SK7 is selected as the reference source.
When the link is removed completly the internal reference of the AD7899 is used as the reference source.
LK3 This link selects the source of the +12V supply.
When this link is in position "A" an external +12V must be connected to J2-1.
When this link is in position "B" the EVAL-BOARD CONTROLLER will provide the +12V supply
LK4 This link selects the source of the VDD supply.
When this link is in position "A" an external +5V must be connected to J2-2.
When this link is in position "B" the EVAL-BOARD CONTROLLER will provide the +5V supply
LK5 This link selects the source of the -12V supply.
When this link is in position "A" an external -12V must be connected to J2-4.
When this link is in position "B" the EVAL-BOARD CONTROLLER will provide the -12V supply
is connected to V
INB
is connected toAGND.
INB
INA
.
LK6 This link selects the source of the V
When this link is in position A the VDD supply is used as the V
DRIVE
supply.
DRIVE
supply.
When this link is in position B the DVDD supply of the EVAL-BOARD CONTROLLER is used as the
V
supply.
DRIVE
When this link is in position C an external supply on SK6 is used as the V
LK7 This link is used to select the source of the Conversion Start signal.
When this link is in position "A" the CONVST signal is generated by the EVAL-BOARD CONTROLLER.
When this link is in position "B" the CONVST signal is generated by an external signal connected to SK2.
LK8 This link selects the source of the CLKIN signal for the AD7899.
When this link is in position "A" the CLKIN signal is provided by the EVAL-BOARD CONTROLLER.
When this link is in position "B" the CLKIN signal can be provided by a signal applied to SK3. If no
signal is applied to SK3 the pin is pulled low and the internal oscillator is is used to control the conversion.
LK9 This link sets the logic level of the STBY pin.
When a link is in position "A" the STBY pin is controlled by the FL1 flag pin of the EVAL-BOARD
CONTROLLER.
When a link is in position "B" the STBY pin is tied to VDD and the part is in normal operating mode.
When a link is in position "C" the STBY pin is tied to DGND and the part is in standby mode.
DRIVE
supply.
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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
shipped. The board is compatible with the EVAL-BOARD CONTROLLER when shipped.
Table I. Initial Link and Switch Positions
Link No. Position Function.
LK1 B The largest voltage range for the part is selected.
LK2 A The AD780 is selected as the reference source for the AD7899.
LK3-5 B The EVAL-BOARD CONTROLLER is used to provide the supply voltages for the
evaluation board.
LK6 A The V
LK7 B The CONVST signal is provided by the EVAL-BOARD CONTROLLER.
LK8 B The CLKIN can be supplied either by an external signal connected to SK3 or by the
AD7899s internal oscillator.
LK9 B The STBY pin is tied to VDD
pin is connected to the VDD supply.
DRIVE
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EV AL-AD7899CB
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 EVALBOARD CONTROLLER or other system. The pinout for
the J1 connector is shown in Figure 2 and its pin designations
are given in Table II.
1
A
B
C
1
Fig. 2. Pin Configuration for the 96-Way Connector, J1
96-Way Connector Pin Description
32
32
FL1 Flag one. This is a logic input and is connected
to the STBY pin of the AD7899. A logic high on
this pin allows normal operation of the AD7899.
A logic low on this pin puts the AD7899 into
standby mode.
D0-D13 Data Bit 0 to Data Bit 13. Bi-directional data
pins. These data bits provide the ADC conversion
results during a read operation.
RD Read. This is an active low logic input which is
used in conjunction with the CS pin to enable the
data outputs.
WR Write. A logic input. A rising edge on this input,
with
CS low and RD high latches the logic state
on D0-D3 into the channel select register. Software selection of channels is not supported by this
evaluation board.
CS Chip Select. An active low logic input. A low
level on this input selects the AD7899.
FL0 Flag zero. This logic input is connected to the
CONVST input of the AD7899 via LK7. A low
to high transition on this input puts all the track/
holds into their hold mode and starts conversion
on the selected channels. In addition the state of
the channel sequence selection is also latched on
the rising edge of this input
IRQ2 Interrupt Request 2. This is a logic output and is
connected to the BUSY logic output on the
AD7899. This output will go high on the rising
edge of CONVST and will return low when
conversion is completed on all selected channels.
DGND 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.
AGND Analog Ground. These lines are connected to the
analog ground plane on the evaluation board.
AV
DD
Analog +5V Supply. These lines are connected to
the V
supply line on the board via LK4.
DD
+12V +12V Supply. This line is connected to the +12V
supply line on the board via LK3.
-12V -12V Supply. This line is connected to the -12V
supply line on the board via LK5.
Table II. 96-Way Connector Pin Functions.
ROW a RowB RowC
1 FL1
2D0
3 SCLK1 D1 SCLK1
4 DGND DGND DGND
5D2
6D3
7D4
8
9RD D5 WR
10 D6 CS
11 D7
12 DGND DGND DGND
13 D8
14 D9
15 D10
16 DGND DGND DGND
17 FL0 D11 IRQ2
18 D12 D13
19
20 DGND DGND DGND
21 AGND AGND AGND
22 AGND AGND AGND
23 AGND AGND AGND
24 AGND AGND AGND
25 AGND AGND AGND
26 AGND AGND AGND
27 AGND
28 AGND
29 AGND AGND AGND
30 -12V AGND +12V
31
32 AVDD AVDD AVDD
Note : The unused pins of the 96-way connector are not shown.
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SOCKETS
There are six input sockets relevant to the operation of the
AD7899 on this evaluation board. The function of these
sockets is outlined in Table III.
Table III. Socket Functions
Socket Function
SK1 Sub-Miniature BNC Socket for the analog
input.
SK2 Sub-Miniature BNC Socket for the exter-
nal reference
SK3 Sub-Miniature BNC Socket for external
V
supply.
DRIVE
SK4 Sub-Miniature BNC Socket for BUSY
output.
SK5 Sub-Miniature BNC Socket for external
CONVST input.
SK6 Sub-Miniature BNC Socket for the exter-
nal CLKIN input.
CONNECTORS
There are two connectors on the AD7899 evaluation board
as outlined in Table IV.
Table IV. Connector Functions
Connector Function
J1 96-Way Connector for Parallel Interface con-
nections.
J2 External +12V, -12V +5V & A
connector.
GND
power
OPERATING WITH THE EVAL-BOARD
CONTROLLER
The evaluation board can be operated in a stand-alone mode
or operated in conjunction with the EVAL-BOARD CONTROLLER. The EVAL-BOARD CONTROLLER is available from Analog Devices under the order entry
"EVAL-BOARD CONTROLLER". When operated with
this control board, all supplies and control signals to operate
the AD7899 are provided by the EVAL-BOARD CONTROLLER. Software to communicate with the Control
Board and AD7899 is provided with the AD7899 evaluation
board package. This EVAL-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-AD7899CB plugs
directly into the 96-way connector on the EVAL-BOARD
CONTROLLER. The EVAL-BOARD CONTROLLER
provides all the supplies for the evaluation board. Itis
powered from a 12VAV transformer. Suitable transformers
are available from Analog Devices as an accessory under the
following part numbers:
EVAL-110VAC-US: For use in the U.S. or Japan
EVAL-220VAC-UK: For use in the U.K.
EVAL-220VAC-EU: For use in Europe
These transformers are also available for other suppliers
including Digikey (U.S.) and Campbell Collins (U.K.).
Connection between the EVAL-BOARD CONTROLLER
and the serial port of a PC is via a standard Centronics printer
port cable which is provided as part the EVAL-BOARD
CONTROLLER package. Please refer to the manual which
accompanies the EVAL-BOARD CONTROLLER for more
details on the EVAL-BOARD CONTROLLER package.
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EV AL-AD7899CB
Figure 2. AD7899 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 1 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 in
question). 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.
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Figure 3. AD7899 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
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
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receive instructions. The 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 connected between the PC and the Evaluation
Board Controller.
Running the Software
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.
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
EV AL-AD7899CB
Figure 4. The Setup Screen
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
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
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 3.
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.
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EV AL-AD7899CB
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:AD7899
programname:ad7899.PRG
samplefrequency:100000
maxsamplefrequency:380000
samples:2048
+/-15V:on
dvdd:5:on
avdd:5:on
bus:on
;options 2scomp, binary
dataformat:2scomp
numberofbits:14
inputVmax:2.5
inputVmin:-2.5
Table VI.: Eval-AD7899CB Bill Of Materials.
Item Qty RefDes Description Manufacturer/Disti Disti Number
1 6 C1 C4 C5 C7 C9 C12 10uF 16V TAJ_B Tantalum cap AVX/FEC FEC 498-737
2 16 C2 C3 C6 C8 C10 C11 C13 C14 100nF 0805 Ceramic Capacitor AVX/FEC FEC 499-687
C15 C16 C18 C20 C22 C24 C26 C28
3 6 C17 C19 C21 C23 C25 C27 47uF 16V TAJ_C Tantalum cap AVX/FEC FEC 197-32
5 3 C30 C31 C32 22pF 0805 Ceramic Capacitor AVX/FEC FEC 317-500
6 2 R1 R2 0W 0.1W 0805 Resistor Multicomp/FEC FEC 772-239
7 3 R3 R4 R5 180W 0.1W 0805 Resistor Multicomp/FEC FEC 911-768
8 1 R6 10kW 0.1W 0805 Resistor Multicomp/FEC FEC 911-975
9 1 J1 DIN41612-96 Harting/FEC FEC 104-986
10 1 J2 4 pin terminal block Augat/FEC FEC 151-787
11 7 LK1 LK2 LK3 LK4 LK5 LK7 LK8 4 pin header (2x2) Harwin/FEC FEC 148-535
12 2 LK6 LK9 6 pin header 3x2) Harwin/FEC FEC 148-535
13 9 LK1-9 "0.1"" pitch Jumper Socket" Harwin/FEC FEC 150-410
14 6 SK1 SK2 SK3 SK4 SK5 SK6 50W SMB socket (vertical) MACOM/FEC FEC 310-682
15 1 U1 AD7899AR-1 Analog Devices ADI Free Issue
16 1 U2 74HC04N Philips/FEC FEC 380-362
17 1 U3 AD845KN Analog Devices ADI Free Issue
18 1 U4 AD780AN Analog Devices ADI Free Issue
19 2 U5 U6 74HC541D Philips/FEC FEC 492-607
20 1 U1 28 pin SOIC Socket Yamaichi/Radiatron IC179-28375-300
21 1 U2 14 pin DIP solder socket Harwin/FEC FEC 738-529
22 16 U3 U4 Ultra low profile sockets Harwin/FEC FEC 519-935
23 4 Rubber stick-on feet 3M/FEC FEC 148-922
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Figure 5. AD7899 Evaluation Board Circuit Diagram.
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Figure 6. Component Side Artwork.
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Figure 7. Solder Side Artwork.
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EV AL-AD7899CB
Figure 8. Component Side Silkscreen Artwork.
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