EVAL-AD7714-5EB Evaluation Board for Signal

EVAL-AD7714-5EB Evaluation Board for Signal
a
Evaluation Board for
Signal Conditioning ADC
EVAL-AD7714-5EB
FEATURES
OPERATING THE AD7714-5 EVALUATION BOARD
Operates from a Single +5V Supply
Power Supplies
The evaluation board has four power supply input pins: AVDD,
AGND, DVDD and DGND. The AD7714-5 is specified with an
AVDD of +5V. Therefore, the AVDD voltage supplied to the
board must be +5V. This AVDD voltage is also used to power the
AD780 reference. The AD7714-5 can be operated from a +5V
or +3V DVDD voltage. When using the 9-way D-type connector
to interface to the evaluation board it is possible to apply a
DVDD voltage of either +3V or +5V to the DVDD input terminal
on the board. However, when using the 36-way Centronics
connector to interface to the board, the voltage applied to the
DVDD input terminal must be +5V. This is because the
Centronics connector is intended for connection to the printer
port of a PC with signals driven from +5V supplies. To run the
board from a single +5V supply, simply connect the AVDD and
DVDD inputs together.
On-Board Reference and Digital Buffers
Various Linking Options
Direct Hook-Up to Printer Port of PC
PC Software for Control and Data Analysis
INTRODUCTION
This Application Note describes the evaluation board for the
AD7714-5, 24-Bit signal conditioning ADC. The AD7714 is a
complete analog front end for low-frequency applications
providing either three fully-differential or five pseudodifferential input channels. The device accepts low-level signals
directly from a transducer and outputs a serial digital word. It
employs a sigma delta technique to realize up to 24 bits of no
missing codes performance. Full data on the AD7714-5 is
available in the AD7714 data sheet available from Analog
Devices and should be consulted in conjunction with this
Application Note when using the Evaluation Board.
Included on the evaluation board, along with the AD7714-5, are
an AD780, a +2.5 V ultra high precision bandgap reference, a
2.4576MHz crystal and digital buffers to buffer signals to and
from the edge connectors.
Interfacing to this board is provided either through a 36-Way
Centronics Connector or through a 9-way D-type connector.
External sockets are provided for the analog inputs, an external
reference input option and an external master clock option.
Both AGND and DGND inputs are provided on the board.
AGND connects to the AD7714-5 AGND pin and also connects to the GND pin of the AD780. DGND connects to the
DGND pin of the AD7714 and to the GND of the digital chips
on the board. The AGND and DGND planes are connected at
the AD7714. Therefore, it is recommended not to connect
AGND and DGND elsewhere in the system to avoid ground
loop problems. When using a single supply for both AVDD and
DVDD, only one ground connection should be made to the
board. This connection should be made to the board's AGND
input terminal.
Both supplies are decoupled to their respective ground plane
with 10µF tantalum and 0.1µF ceramic disc capacitors.
FUNCTIONAL BLOCK DIAGRAM
AVDD
AGND
DVDD
DGND
9-WAY D-TYPE CONNECTOR
AIN1
AIN2
AIN3
AD7714
ADC
BUFFERS
AIN4
36-WAY
CENTRONICS
CONNECTOR
AIN5
AIN6
AD780
REFERENCE
REF IN
MCLK IN
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
EVAL-AD7714-5EB
Link Options
There are a number of link options on the evaluation board which should be set for the required operating setup before using the
board. The functions of these link options are described in detail below.
Link No.
Function
LK1
This option selects the master clock option for the AD7714. The master clock source comes from the on-board
crystal or from an external clock source via SKT6. This is a double link and both links must be moved together for
correct operation.
With both links in position A, the external clock option is selected and an externally applied clock to SKT 6 is routed
the MCLK IN pin of the AD7714.
With both links in position B, the on-board crystal is selected and provides the master clock for the AD7714.
LK2
This link option is used to determine whether the AD7714 is in its normal operating mode or its STANDBY (power
down) mode.
With this link in position A, the STANDBY input is connected to a logic high thus configuring the part for normal
operation.
With this link in position B, the STANDBY pin is connected to a logic low and the AD7714 is placed in its power
down mode where its power dissipation is typically 100µW.
LK3
This link option is used to control the buffer option input on the AD7714 (i.e. determine the voltage on the AD7714
BUFFER pin).
With this link in position A, a logic high is connected to this input. This connects the on-chip buffer in series with the
analog input which allows the inputs to handle higher source impedance.
With this link in position B, a logic low is connected to the buffer option select input. With this input low, the on-chip
buffer on the analog input is shorted out.
LK4
This link controls the polarity of the serial clock.
With this link in position A, the POL pin is connected to a logic high. With this input high, the first transition of the
serial clock in a data transfer operation is from a high to a low.
With this link in position B, the POL input is connected to a logic low and the first transition of the serial clock in a
data transfer operation is from a low to a high.
LK5
This link option is used to select the reference source for the AD7714's REF IN(-) input.
With this link in position A, the REF IN(-) pin of the AD7714 is connected directly to AGND.
With this link in position B, the REF IN(-) pin of the AD7714 is connected to SKT10. An external voltage connected
to SKT10 can now be used for REF IN(-).
LK6
This link option is used to select the reference source for the AD7714's REF IN(+) input.
With this link in position A, the REF IN (+) pin of the AD7714 is connected directly to the output of the on-board
reference, the AD780.
With this link in position B, the REF IN(+) pin of the AD7714 is connected to SKT9. An external voltage connected
to SKT 9 can now be used for REF IN(+).
LK7
This link option is set depending on the type of reference being used on the evaluation board. Although the board is
equipped with an AD780, a REF-192 +2.5V reference can replace it in the same socket. When a REF-192 reference
is used on the board, the link should be in position A. In position A, the REF-192's shutdown pin is connected to the
STANDBY pin of the AD7714 and is controlled by LK2.
When the AD780 reference is used, the link should be in position B as the AD780 does not have a shutdown pin.
LK8-LK13
These links are in series with the AIN 1 through AIN 6 analog inputs respectively.
With these links in place, the analog input on the relevant SKT input is connected directly to the respective AIN
input on the part. For example, with LK8 in place, the analog signal applied to SKT7 is connected directly to AIN6
of the AD7714.
These links may be removed so that the input signals at the AIN SKTs can be connected to the component grid for
signal conditioning before being applied to the analog inputs of the AD7714.
–2–
REV. A
EVAL-AD7714-5EB
Setup Conditions
Table I shows the position in which all the links are set when the
evaluation board is sent out.
1
Table I. Initial Link Positions
Link No.
Position Function.
LK1
B
LK2
A
LK8-LK13 IN
Figure 2. SKT1 Pin Configuration
Table II. SKT1 Pin Designations1
2
DRDY
Logic Output. This is a buffered version of the
signal on the AD7714's DRDY pin.
3
CS
Chip Select. The signal on this pin is buffered
before being applied to the CS pin of the
AD7714.
4
RESET
Reset Input. The signal on this pin is buffered
before being applied to the RESET pin of the
AD7714.
5
DIN
Serial Data Input. Data applied to this pin is
buffered before being applied to the AD7714's
DIN pin.
6
DGND
Ground reference point for digital circuitry.
Connects to the DGND plane on the evaluation
board.
7
DOUT
Serial Data Output. This is a buffered version of
the signal on the AD7714's DOUT pin.
8
DVDD
Digital Supply Voltage. If no DVDD voltage is
applied to the board's DVDD input terminal,
then the voltage applied to this pin of the connector will supply the DVDD for the evaluation
board.
9
SYNC
Logic Input. The signal on this pin is buffered
before being applied to the SYNC pin of the
AD7714.
Connects POL pin high such that the
first transition of the serial clock in a
data transfer is from a high to a low.
B
REF IN(-) connected directly to
AGND.
REF IN(+) connected to the output of
the on-board AD780 reference.
Selects AD780 as the voltage reference.
Connects analog inputs from the input
sockets directly to the respective analog
input pins of the AD7714.
EVALUATION BOARD INTERFACING
Interfacing to the evaluation board is either via a 36-way
Centronics connector,SKT11, or a 9-way D-Type connector,
SKT1. The pinout for the SKT1 connector is given in Figure 1
and its corresponding pin designations are given in Table II.
The pinout for this SKT11 connector is shown in Figure 2 and
its pin designations are given in Table III. The evaluation board
should be powered up before a cable is connected to either of
the connectors.
NOTE
1
An explanation of the AD7714 functions mentioned here is given in Table III as
part of the SKT11 pin designations description.
SKT11 is used to connect the evaluation board to the printer
port (parallel port) of a PC. Connection between the two is
direct via a standard parallel printer port cable. SKT1 is used to
connect the evaluation board to any other system.
REV. A
9
Serial Clock. The signal on this pin is buffered
before being applied to the SCLK pin of the
AD7714.
A
LK7
8
5
SCLK
LK4
A
7
4
1
The on-chip buffer on the AD7714 is
shorted out.
LK6
3
Connects STANDBY high and thus
configures the part for normal
operation.
B
A
6
Both links in position B to select the
on-board crystal oscillator as the master
clock for the board.
LK3
LK5
2
–3–
EVAL-AD7714-5EB
18
1
36
19
Figure 3. SKT11 Pin Configuration
Table III. SKT11 Pin Designations
1
NC
No Connect. This pin is not connected on the evaluation board.
2
DIN
Serial Data Input. Data applied to this pin is buffered before being applied to the AD7714's DIN pin. The
serial data applied to the DIN pin is written to the input shift register on the part. Data from this input shift
register is transferred to the calibration registers, mode register, communications register or filter selection
registers depending on the register selection bits of the Communications Register.
3
RESET
Reset Input. The signal on this pin is buffered before being applied to the RESET pin of the AD7714.
RESET is an active low input which resets the control logic, interface logic, calibration coefficients, digital
filter and analog modulator of the part to power-on status.
4
CS
Chip Select. The signal on this pin is buffered before being applied to the CS pin of the AD7714. CS is an
active low logic input used to select the AD7714. With this input hard-wired low, the AD7714 operates in its
three-wire interface mode with SCLK, DIN and DOUT used to interface to the device. CS can be used to
select the device in systems with more than one device on the serial bus or as a frame synchronisation signal
in communicating with the AD7714.
5
SCLK
Serial Clock. The signal on this pin is buffered before being applied to the SCLK pin of the AD7714. An
external serial clock is applied to this input to access serial data from the AD7714. This serial clock can be a
continuous clock with all data transmitted in a continuous train of pulses. Alternatively, it can be a non-continuous clock with the information being transmitted to the AD7714 in smaller batches of data.
6
SYNC
Logic Input. The signal on this pin is buffered before being applied to the SYNC pin of the AD7714. The
SYNC input allows for synchronisation of the digital filters and analog modulators across a number of
AD7714s. While SYNC is low, the nodes of the digital filter, the filter control logic and the calibration
control logic are reset and the analog modulator is also held in its reset state.
7-8
NC
No Connect. These pins are not connected on the evaluation board.
9
DVDD
Digital Supply Voltage. This provides the supply voltage for IC4, the buffer chip which buffers the output
signals from the AD7714 before they are applied to SKT11.
10
DRDY
Logic output. This is a buffered version of the signal on the AD7714's DRDY pin. A logic low on the DRDY
output indicates that a new output word is available from the AD7714 data register. The DRDY pin will
return high upon completion of a read operation of a full output word. If no data read has taken place, after
an output update, the DRDY line will return high for 500* tCLK IN cycles prior to the next output update.
This gives an indication of when a read operation should not be attempted to avoid reading from the data
register as it is being updated. DRDY is also used to indicate when the AD7714 has completed its on-chip
calibration sequence.
11-12
NC
No Connect. These pins are not connected on the evaluation board.
13
DOUT
Serial Data Output. This is a buffered version of the signal on the AD7714's DOUT pin. Serial data from
the output shift register on the part is clocked out on this pin. This output shift register can contain information from the calibration registers, mode register, communications register, filter selection registers or data
register depending on the register selection bits of the Communications Register.
14-18
NC
No Connect. These pins are not connected on the evaluation board.
19-30
DGND
Ground reference point for digital circuitry. Connects to the DGND plane on the evaluation board.
31-36
NC
No Connect. These pins are not connected on the evaluation board.
–4–
REV. A
EVAL-AD7714-5EB
SOCKETS
There are eleven sockets on the AD7714-5 evaluation board.
The function of these sockets is outlined in Table IV.
Table IV. Socket Functions
Socket
Function
SKT1
9-Way D-Type Connector which can be used for
digital interfacing to the evaluation board.
SKT2
Sub-Minature BNC Connector. The analog input
signal for the AIN1 input of the AD7714 is applied
to this socket.
SKT3
Sub-Minature BNC Connector. The analog input
signal for the AIN2 input of the AD7714 is applied
to this socket.
SKT4
Sub-Minature BNC Connector. The analog input
signal for the AIN3 input of the AD7714 is applied
to this socket.
SKT5
Sub-Minature BNC Connector. The analog input
signal for the AIN4 input of the AD7714 is applied
to this socket.
SKT6
Sub-Minature BNC Connector. The master clock
signal for the MCLK IN input of the AD7714 is
applied to this socket when the board is configured
for an externally-applied master clock.
SKT7
Sub-Minature BNC Connector. The analog input
signal for the AIN6 input of the AD7714 is applied
to this socket.
SKT8
Sub-Minature BNC Connector. The analog input
signal for the AIN5 input of the AD7714 is applied
to this socket.
SKT9
Sub-Minature BNC Connector. The reference
voltage for the REF IN(+) input of the AD7714 is
applied to this socket when the board is configured
for an externally-applied reference voltage.
SKT10
Sub-Minature BNC Connector. The reference
voltage for the REF IN(-) input of the AD7714 is
applied to this socket when the board is configured
for an externally-applied reference voltage.
SKT11
36-Way Centronics Connector which can be used
for digital interfacing to the evaluation board. This
connector should be used when connecting the
board to the parallel printer port of the PC to use
the evaluation software.
RUNNING THE AD7714 INTERFACE SOFTWARE.
Included in the evaluation board package is a PC-compatible
disk which contains software for controlling and evaluating the
performance of the AD7714 using the printer port of a PC.
There are two files on the disk, an executable file and a
"README" text file which gives details of the functions
available in the executable program. The executable program
runs under DOS and it is advised that the user copies this file to
the system hard disk to obtain optimum performance from the
software.
REV. A
To run the evaluation software simply run the executable file.
The program provides a number of different menu-type screens,
each screen containing several function options. On each of
these menu-screens the user can choose the function by pressing
the associated number key or click on the required option using
the mouse. Alternatively, the user can scroll up or down the
screen using the arrow keys to the required function and then
hit the RETURN key. The "README" file gives a detailed
description of each of the menus and the procedure to use the
software to evaluate the board. A brief description of the
procedure is outlined below.
PC Configuration
The first menu gives options on the type of PC being used. The
printer port needs to be configured correctly for one of the many
different PC-types for interfacing to the AD7714. Choose the
required printer type from the menu. The next menu gives
options on the port address to be used. Choose the required
port address. The PC printer port is now configured for
operation with the AD7714 evaluation board.
AD7714 Configuration
The next menu in the sequence is the Main Menu which
contains 6 options. These allow reading from the data register,
configuration of the communications register, file options (read
and write data to files), noise analysis, printer port setup and
resetting the AD7714.
The first option to select in this Main Menu is option 1
(Communications Register). This calls up the Comms
Register Menu which has 8 options.
The first option to select in the Comms Register Menu is
option 0 (Channel Selection) which allows the user to set up
the required analog input channel. After selecting the desired
channel pair in the Channel Configuration Menu, the
program returns to the Main Menu. Select option 1 (Filter
Registers) which allows the user to enter the clock frequency
being used, program the filter cutoff, data word length required
and bipolar or unipolar operation.
After selecting all the required parameters in the Filter Registers Menu, choose option 6 (Exit) to return to the Comms
Register Menu. In this menu select option 2 (Mode Register). This brings up the Mode Register Menu which allows
the gain of the PGA to be programmed, turns on/off the
burnout current, allows software filter synchronization and
allows the various calibration modes to be selected. Calibration
should be the last operation to be completed. When calibration
is complete, choose option 9 (Exit) to return to the Comms
Register Menu. All parameters on the part should now be set
up, so choose option 8 (Exit) to return to the Main Menu.
From the Main Menu select the option 0 (Read from Data
Register). The number of readings required is prompted and as
the read operation proceeds the value read from the AD7714's
data register is displayed on the screen.
Data Analysis
When all the data has been read, the program returns the user
to the Main Menu. It is possible to write the data which has
been read to a file by selecting option 2 (Files Option) or
analyze the data by selecting option 3 (Do Noise Analysis).
The Noise Menu allows the user to get statistical results from
the data, to plot the raw data, plot a histogram of the data on
the screen or perform a rolling average on the data. To return to
the Main Menu from the Noise Menu choose option 5 (Exit).
–5–
EVAL-AD7714-5EB
5V
36 PIN CENTRONICS CONNECTOR
D7
9
D1
HP 5082- 2810
SKT 11
D4
ACK SLCT
D3
GND
6
10
5
13
19 - 30
SCLK SYNC DRDY DOUT DGND
D2
4
RESET CS
D0
2
DIN
D1
3
DV
DD
R12 10kΩ
R7 10kΩ
R6 10kΩ
74HCT244
IC5
11
8
4
6
2
19
20
10
1
C18
0.1µF
9
12
14
16
18
8
D2
HP 5082- 2810
DV DD
6 DGND
3
14
R5 3kΩ
11
4
1
11
21
B
4
DV
DD
12
2
13
1
12
7
IC4
74HC08
3
2
3
10
9
14
15
2
6
7
1
4
5
DOUT
CS
SKT1
CS
6 RESET
A
C19
0.1µF
19
DOUT
SW 1
RESET
7
0.1µF
C10
DIN
22
DRDY
20
SCLK
1
POL
IC3
74HC4050
5
DIN
DRDY
SCLK
LK4
24 DGND
DGND
5
SYNC
18 AGND
AGND
B
LK 10
7
R1
LK1
AIN1
SKT6
C11
IC1
AD7714
LK 11
R10
B
8
SKT3
R2
A
AIN 2
C12
MCLK OUT
C17
C16
3
XTAL1
LK 12
9
SKT4
R3
A
AIN 3
LK 13
LK3
DV
DD
10 AIN 4
R4
B
BUFFER 13
C13
SKT5
C14
LK8
AIN 6 16
SKT7
C8
R8
LK 9
LK5
17 AIN 5
SKT8
R9
SYNC
A
2
MCLK IN
SKT2
9
8
A
C7
REF IN(-)
B
14
SKT10
AVDD
12 AV
C5
10µF
C6
0.1µF
DD
LK6
DV
DD
C3
10µF
C4
0.1µF
A
23 DV
10
DD
REF IN(+)
B
15
C8
0.1µF
STANDBY
11
SKT9
6
LK2
A
DV
3
DD
B
B
LK7
A
IC2
AD780/
REF-192
4
AV
DD
2
C1
10µF
C2
0.1µF
Figure 3. AD7714-5 Evaluation Board Circuit Diagram
–6–
REV. A
EVAL-AD7714-5EB
COMPONENT LISTING AND MANUFACTURERS
Intergrated Circuits
Component
Location
Vendor
AD7714
IC1
Analog Devices
AD780
IC2
Analog Devices
74HC4050
IC3
Motorola
74HCT08
IC4
Motorola
74HCT244
IC5
Integrated Device Technology
HP 5082-2810
D1 & D2
Hewlett Packard
Component
Location
Vendor
10µF ± 20% Tantalum (16 V)
C1, C3, C5
AVX- Kyocera
Mftrs No TAG106MO16
0.1µF Ceramic(X7R ± 20%)
C2, C4, C6, C9,
C10, C15, C18, C19
Philips
Mftrs No. CW20C 104M
33pF ± 2% Ceramic
C16, C17
Philips
Mftrs No. 683 34339
Open Circuit
C7, C8, C11, C12,
C13, C14
Capacitors
Resistors
Component
Location
Vendor
10kΩ ± 5% 0.25W
Carbon Film Resistor
R5, R6, R7, R12
Bourns
1MΩ± 5% 0.25W
Carbon Film Resistor
R10
Bourns
Short Circuits
R1, R2, R3, R4,
R8, R9.
Link Options
Component
Location
Vendor
Pin Headers
Lk1 (4x2 way)
Harwin
Lk2, Lk3, Lk4,
Lk5, Lk6, Lk7
( 2x2 way)
Mftrs No. M20-9993606
Lk8, Lk9, Lk10,
Lk11, Lk12, Lk13
(1x2 way)
Shorting Plugs
REV. A
Pin Headers
(14 required)
Harwin
Mftrs No. M7571-05
–7–
EVAL-AD7714-5EB
Switch
Component
Location
Vendor
Push Button Switch
SW1
Omron
Mftrs No. B3F1000
Component
Location
Vendor
Miniature BNC Connectors
SKT2 - SKT 10
M/A - Com Greenpar
Mftrs No. C65N07G999X99
9-Way D-Type Connector
SKT1
McMurdo
Mftrs No. SDE9PNTD
36 Way Centronics Connector
SKT 11
Fujitsu
Mftrs No. FCN785J036G0
Sockets
24-Pin IC Socket
IC1
Harwin
8 Pin IC Socket
IC2
Mftrs No. D28xx-01
16-Pin IC Socket
IC3
xx = No. of Pins
14- Pin IC Socket
IC4
20-Pin IC Socket
IC5
Wire Wrap Pins
DGND, AGND, AVDD,
DVDD
Bicc Vero
Mftrs No. 663472C
Component Identification
Location
Vendor
2.4576MHz Oscillator
Xtal 1
IQD
Mftrs No. A166C
Crystal Oscillator
–8–
REV. A
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