Analog Devices AD7707EB Datasheet
Evaluation Board for the AD7707 3V/5V, +/-10V Input
a
Range, 1mW, 3Channel, 16-Bit, Sigma Delta ADC
FEATURES
Full-Featured Evaluation Board for the AD7707
On-Board Reference and Digital Buffers
Various Linking Options
PC Software for Control of AD7707
On-Board Patchwork Area
INTRODUCTION
This Technical Note describes the evaluation board for the
AD7707, 3V/5V, +/-10V Input Range, 1mW, 3 Channel, 16Bit, Sigma Delta ADC. The AD7707 is a complete analog
front end for low frequency measurement applications. This
three-channel device can accept either low level input signals
directly from a transducer or high level (± 4 x VBIAS) signals
and produce a serial digital output. The AD7707 operates
from a single 2.7V to 3.3V or 4.75V to 5.25V supply. The
AD7707 features two low level pseudo-differential analog
input channels, one high level input channel and a differential
reference input. Full data on the AD7707 is available in the
AD7707 datasheet available from Analog Devices and should
be consulted in conjunction with this Technical Note when
using the evaluation board.
The evaluation board interfaces to the parallel port of an IBM
compatible PC. Software is available with the evaluation
board which allows the user to easily program the AD7707.
EVAL-AD7707EB
Other components on the AD7707 Evaluation Board include
an AD780 (a precision 2.5V reference), an AD589 (a 1.23V
precision bandgap reference), a 4.9152 MHz crystal and
digital buffers to buffer signals to and from the PC.
OPERATING THE AD7707 EVAL BOARD
Power Supplies
This evaluation board has two analog power supply inputs:
AV
and AGND. An external +5V or +3V must be applied
DD
between these inputs which is used to provide the AV
AD7707 and the reference. DGND and DV
are also available. The DV
the AD7707 DV
pin and the digital circuitry. When AV
DD
is used to provide the DVDD for
DD
DD
is set to +5V, DVDD can be +3V or +5V. When AVDD is set
to +3V, DV
AV
. DGND and AGND are connected together under the
DD
can only be +3V. DVDD should never exceed
DD
AD7707. Therefore, it is recommended not to connect
AGND and DGND elsewhere in the system.
All power supplies are decoupled to their respective grounds.
DV
is decoupled using a 10µF tantalum capacitor and
DD
0.1µF ceramic capacitor as close as possible to the AD7707
pin. It is again decoupled using 0.1µF capacitors as
DV
DD
close as possible to each logic device. AV
DD
using a 10µF tantalum capacitor and 0.1µF ceramic capacitor as close as possible to the AD7707 and also at the
reference.
for the
DD
connections
DD
is decoupled
Figure 1: Evaluation Board Setup
DV
36-WA Y
CENTRO NICS
CONNE CTOR
9-WAY D-TYPE CONNECTOR
DGND
DD
BUFFERS
AGND
CRYSTAL
AD7707
ADC
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.
VREF-
AV
DD
AGND
MCLK IN
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
VREF+
REFERENCE
REFERENCE
AIN1 AIN2
AD1580
AD780
AIN3
HBIAS
HCOMLCOM
EVAL-AD7707EB
LINK AND SWITCH OPTIONS
There are ten link options which must be set for the required operating setup before using the evaluation board. The functions
of these link options are outlined below.
Link No. Function
LK1 This option selects the master clock source for the AD7707. The master clock is generated by the on-board crystal
or from an external source via SKT11. This is a double link and both links must be moved together for the correct
operation of the evaluation board.
With both links in position "A", the external clock option is selected and an external clock applied to SKT11 is
routed to the MCLKIN pin of the AD7707.
With both links in position "B", the on-board crystal is selected to provide the master clock to the AD7707.
LK2 This link is used to select the on-board reference.
With this link in position "A", the AD780 is selected as the on-board reference. This provides a 2.5V reference
which is suitable for the AD7707 operating at +5V.
With this link in position "B", the AD589 is selected as the on-board reference. This provides a 1.23V reference
which is suitable for the AD7707 operating at +3V.
LK3 This link is used to select the reference source for the REFIN(-) input of the AD7707.
With this link in position"A", the REFIN(-) pin is connected directly to AGND.
With this link in position "B", the REFIN(-) pin is connected to SKT10. An external voltage applied to SKT10
can now be used as the REFIN(-) for the AD7707.
LK4 This link is used to select the reference source for the REFIN(+) input of the AD7707.
With LK4 in position "A", the REFIN(+) pin is connected to the output of the on-board reference.
With LK4 in position "B", the REFIN(+) pin is connected to SKT9. An external voltage applied to SKT9 can
now be used as the REFIN(+) for the AD7707.
LK5 This link is in series with the AIN1 input of the AD7707.
With this link in place, an analog input signal applied to SKT3 is routed directly to the AIN1 pin of the AD7707.
This link may be removed so that the user can add signal conditioning circuitry if required.
LK6 This link is in series with the AIN2 input of the AD7707.
With this link in place, an analog input signal applied to SKT4 is routed directly to the AIN2 pin of the AD7707.
This link may be removed so that the user can add signal conditioning circuitry if required.
LK7 This link is in series with the AIN3 input of the AD7707.
With this link in place, an analog input signal applied to SKT5 is routed directly to the AIN3 pin of the AD7707.
This link may be removed so that the user can add signal conditioning circuitry if required.
LK8 This link is used to select the common input for low level input channels (AIN1 and AIN2).
With this link in position "A", the LCOM input is tied to AGND.
With this link in position "B", the LCOM input is tied to VREF.
With this link in position "C", the LCOM input is set to a voltage applied to SKT6.
LK9 This link is connected to the HBIAS pin. It used to signal condition the high level input channel (AIN3).
With this link in positoin "A", the HBIAS pin is tied to the REFIN+ pin of te AD7707.
With this link in position "B", a voltage applied to SKT7 is applied to the HBIAS pin.
LK10 This link is connected to the HCOM pin of the AD7707. It stes the common input voltage for the high level input
channel (AIN3).
With this link in position "A", the HCOM input is tied to AGND.
With this link in position "B", the HCOM input is tied to VREF.
With this link in position "C", the HCOM input is set to a voltage applied to SKT8.
- 2 -
Rev. 0
EVAL-AD7707EB
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 1 shows the position in which all the links are set when the evaluation board is sent out.
Table 1: Initial Link and Switch Positions
Link No. Position Function
LK1 B+B Both links in position "B" to select the on-board crystal as the master clock for the AD7707.
LK2 A This selects the AD780 +2.5V output as the on-board reference.
LK3 A This connects the REFIN(-) input of the AD7707 to AGND.
LK4 A The on-board reference provides the reference voltage for the REFIN(+) input of the AD7707.
LK5 IN The AIN1 pin on the AD7707 is tied to the analog input sockets SKT3.
LK6 IN The AIN2 pin on the AD7707 is tied to the analog input sockets SKT4.
LK7 IN The AIN3 pin on the AD7707 is tied to the analog input sockets SKT5.
LK8 A The LCOM pin on the AD7707 is tied to the AGND.
LK9 A The HBIAS pin of the AD7707 is tied to the REFIN+ pin.
LK10 A The HCOM pin on the AD7707 is tied to the AGND.
EVALUATION BOARD INTERFACING
Interfacing to the evaluation board is via either a 9-way d-type connector, SKT1 or a 36-way centronics connector, SKT2.
The pin-out for the SKT1 connector is shown in Fig. 2 and its pin designations are given in Table 2. The pin-out for the
SKT2 connector is shown in Fig. 3 and its pin designations are given in Table 3.
SKT2 is used to connect the evaluation board to the parallel (printer) port of a PC. Connection is via a standard printer cable.
SKT1 is used to connect the evaluation to any other system. The evaluation board should be powered up before a cable is
connected to either of these connectors.
2431
5
6789
Fig. 2: Pin Configuration for the 9-Way D-Type Connector, SKT1.
Table 2.: SKT1 Pin Description
1
1 SCLK Serial Clock. The signal on this pin is buffered before being applied to the SCLK pin of the AD7707.
2 DRDY Logic output. This is a buffered version of the signal on the AD7707 DRDY pin
3 CS Chip Select. The signal on this pin is buffered before being applied to the CS pin on the AD7707.
4 RESET Reset Input. Data applied to this pin is buffered before being applied to the AD7707 RESET pin.
5 DIN Serial Data Input. Data applied to this pin is buffered before being applied to the AD7707 DIN pin.
6 DGND Ground reference point for the 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 AD7707 DOUT pin.
8DV
Digital Supply Voltage. If no voltage is applied to the board's DVDD input terminal then the voltage applied to
DD
this pin will supply the DV
for the digital buffers.
DD
9 NC Not Connected.
Note
1
An explanation of the AD7707 functions mentioned here is given in Table 3 overleaf as part of the SKT2 pin descriptions.
- 3 -
Rev. 0
EVAL-AD7707EB
18
36
Fig. 3: 36-way Centronics (SKT2) Pin Configuration
Table 3: 36-Way Connector Pin Description
1 NC No Connect. This pin is not connected on the evaluation board.
2 DI N Serial Data Input. Data applied to this pin is buffered before being applied to the AD7707 DIN pin.
Serial Data Input with serial data being written to the input shift register on the part. Data from this
input shift register is transferred to the setup register, clock register or communications register
depending on the register selection bits of the Communications Register.
3
4
5 S CL K Serial Clock. The signal on this pin is buffered before being applied to the SCLK pin of the AD7707.
6-8 NC No Connect. These pins are not connected on the evaluation board.
9DV
10
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 AD7707 DOUT pin. Serial Data
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.
RESET Reset Input. The signal on this pin is buffered before being applied to the RESET pin of the AD7707.
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.
CS Chip Select. The signal on this pin is buffered before being applied to the CS pin of the AD7707.
CS is an active low Logic Input used to select the AD7707. With this input hard-wired low, the
AD7707 can operate in its three-wire interface mode with SCLK, DIN and DOUT used to interface
to the device.
bus or as a frame synchronization signal in communicating with the AD7707.
An external serial clock is applied to this input to read/write serial data from/to the AD7707. This
serial clock can be continuous with all data transmitted in a continuous train of pulses. Alternatively,
it can be non-continuous with the information being transmitted to the AD7707 in smaller batches
of data.
DD
DRDY Logic output. This is a buffered version of the signal on the AD7707 DRDY pin. A logic low on
Digital Supply Voltage. This provides the supply voltage for the buffer chips, U3-U5, which buffer
the signals between the AD7707 and SKT1/SKT2.
this output indicates that a new output word is available from the AD7707 data register. The
pin will return high upon completion of a read operation of a full output word. If no data read has
taken place between output updates, the
to the next output update. While
reading from the data register as it is being updated. The
the update has taken place.
on-chip calibration sequence.
Output with serial data obtained from the output shift register on the AD7707. The output shift
register can contain information from the setup register, communications register, clock register or
data register depending on the register selection bits of the Communications Register.
CS can be used to select the device in systems with more than one device on the serial
DRDY line will return high for 500 x CLK
DRDY is high, a read operation should not be attempted to avoid
DRDY is also used to indicate when the AD770-55 has completed its
1
19
DRDY
cycles prior
IN
DRDY line will return low again when
- 4 -
Rev. 0
EVAL-AD7707EB
SOCKETS
There are eleven sockets relevant to the operation of the
AD7707 on this evaluation board. The functions of these
sockets are outlined in Table 4.
Table 4. Socket Functions
Socket Function
SKT1 9-way D-Type connector used to interface to other
systems.
SKT2 36-way centronics connector used to interface to
PC via parallel printer port.
SKT3 Sub-Miniature BNC (SMB) Connector. The
analog input signal for the AIN1 input of the
AD7707 is applied to this socket.
SKT4 Sub-Miniature BNC (SMB) Connector. The
analog input signal for the AIN2 input of the
AD7707 is applied to this socket.
SKT5 Sub-Miniature BNC (SMB) Connector. The
analog input signal for the AIN3 input of the
AD7707 is applied to this socket.
SKT6 Sub-Miniature BNC (SMB) Connector. The
analog input signal for the LCOM input of the
AD7707 may be applied to this socket.
SKT7 Sub-Miniature BNC (SMB) Connector. The
analog input signal for the HBIAS input of the
AD7707 may be applied to this socket.
SKT8 Sub-Miniature BNC (SMB) Connector. The
analog input signal for the HCOM input of the
AD7707 may be applied to this socket.
SKT9 Sub-Miniature BNC (SMB) Connector. The
reference voltage for the REFIN+ input of the
AD7707 is applied to this socket when the board
is configured for an externally applied reference
voltage.
SKT10 Sub-Miniature BNC (SMB) Connector. The
reference voltage for the REFIN- input of the
AD7707 is applied to this socket when the board
is configured for an externally applied reference
voltage.
SKT11 Sub-Miniature BNC (SMB) Connector. The
master clock signal for the MCLKIN input of the
AD7707 is applied to this socket when the board
is configured for an externally applied master
clock.The AD7707 can be operated with internal
clock frequencies in the range 500kHz to 5MHz.
CONNECTORS
There are two connectors on the AD7707 evaluation board as
outlined in Table 5.
Table 5. Connector Functions
Connector Functions
J1 PCB Mounting Terminal Block. The Digi-
tal Power Supply to the Evaluation Board
must be provided via this Connector if it is
not being supplied via SKT1 or SKT2.
J2 PCB Mounting Terminal Block. The Ana-
log Power Supply to the Evaluation Board
must be provided via this Connector.
SWITCHES
There is one switch on the AD7707 Evaluation board. SW1
is a push-button reset switch. Pushing this switch activates the
active low RESET input on the AD7707 which resets the
control logic, interface logic, calibration coefficients, digital
filter and analog modulator of the part to power-on status.
- 5 -
Rev. 0
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