Analog Devices EVAL-AD7715-5EB Instructions Manual

a
FEATURES
Operates from a Single +5V Supply
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
AD7715-5, 16-Bit signal conditioning ADC. The AD7715 is a
complete analog front end for low-frequency applications
providing a fully-differential input channel. 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
16 bits of no missing codes performance. Full data on the
AD7715-5 is available in the AD7715 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 AD7715-5, 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.
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.
FUNCTIONAL BLOCK DIAGRAM
AV DD AGND
DV DD DGND
AIN(+)
AIN(-)
AD780
REFERENCE
16-Bit Sigma Delta ADC
OPERATING THE AD7715-5 EVALUATION BOARD
Power Supplies
The evaluation board has four power supply input pins: AV
AGND, DV and DGND. The AD7715-5 is specified with an
DD
AV of +5V. Therefore, the AV
DD
board must be +5V. This AV
AD780 reference. The AD7715-5 can be operated from a +5V
or +3V DV voltage. When using the 9-way D-type connector
DD
to interface to the evaluation board it is possible to apply a
DV voltage of either +3V or +5V to the DV
DD
on the board. However, when using the 36-way Centronics
connector to interface to the board, the voltage applied to the
DV input terminal must be +5V. This is because the
DD
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 AV
DV inputs together.
DD
Both AGND and DGND inputs are provided on the board.
AGND connects to the AD7715-5 AGND pin and also con-
nects to the GND pin of the AD780. DGND connects to the
DGND pin of the AD7715 and to the GND of the digital chips
on the board. The AGND and DGND planes are connected at
the AD7715. 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 AV
DV , only one ground connection should be made to the
DD
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.
9-WAY D-TYPE CONNECTOR
AD7715
BUFFERS
ADC
REF IN MCLK IN
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700
Evaluation Board for
EVAL-AD7715-5EB
voltage supplied to the
DD
voltage is also used to power the
DD
input terminal
DD
36-WAY
CENTRONICS
CONNECTOR
Fax: 617/326-8703
,
DD
and
DD
and
DD