Analog Devices EVAL-AD7730LEB, Технические заметки

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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
a
Evaluation Board for
AD7730L Transducer ADC
EVAL-AD7730LEB
FEATURES
Operates from a 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
On-Board User Grid Area for Expansion 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 exter-
nal reference input option and an external master clock
option.
OPERATING THE AD7730L EVALUATION BOARD
POWER SUPPLIES
The evaluation board has four power supply input pins:
AV
DD
, AGND, DV
DD
and DGND. The AD7730L is specified
with an AV
DD
of +5V. Therefore, the AV
DD
voltage supplied
to the board must be +5V. This AV
DD
voltage is also used to
power the AD780 reference. To run the board from a single
+5V supply, simply connect the AV
DD
and DV
DD
inputs
together.
Both AGND and DGND inputs are provided on the board.
AGND connects to the AD7730L AGND pin and also connects
to the GND pin of the AD780. DGND connects to the DGND
pin of the AD7730L and to the GND of the digital chips on the
board. The AGND and DGND planes are connected at the
AD7730L. Therefore, it is recommended not to connect AGND
and DGND elsewhere in the system to avoid ground loop prob-
lems. When using a single supply for both AV
DD
and DV
DD
, 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.
REV. B
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.
INTRODUCTION
This Technical Note describes the evaluation board for the
AD7730L, Transducer ADC. The AD7730L is a complete ana-
log front-end for weigh-scale and pressure measurement applica-
tions. The device accepts low-level signals directly from a trans-
ducer and outputs a serial digital word. The part features two
buffered differential programmable gain analog inputs as well as
a differential reference input. An on-chip 6-bit DAC allows the
removal of TARE voltages. Clock signals for synchronizing ac
excitation of the bridge are also provided. Full data on the
AD7730L is available in the AD7730 data sheet available from
Analog Devices and should be consulted in conjunction with this
Technical Note when using the Evaluation Board.
Included on the evaluation board, along with the AD7730L, 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.
FUNCTIONAL BLOCK DIAGRAM
AD7730
ADC
9-WAY D-TYPE CONNECTOR
36-WAY
CENTRONICS
CONNECTOR
AD780
REFERENCE
AIN1(+)
AIN1(-)
AVDD AGND DVDD
DGND
AIN2(+)/D1
AIN2(-)/D0
REF IN
BUFFERS
MCLK IN
AVDD
ACX
ACX