EVAL-AD7747| Application Note
Evaluation Board for 24-Bit Capacitance-toDigital Converter with Temperature Sensor
EVAL-AD7747
FEATURES
Full-featured evaluation board for the AD7747 PC evaluation software for control and measurement of the AD7747 USB interface with cable
APPLICATIONS
AD7747 performance evaluation Platform to integrate the AD7747 into system design
The part has an on-chip temperature sensor with resolution of 0.1 C and accuracy of 2 C. The on-chip voltage reference and the on-chip clock generator eliminate the need for any external components in most capacitive sensor applications. The part has a standard voltage input that, together with the differential reference input, allows easy interface to an external temperature sensor, such as an RTD, thermistor, or diode. The AD7747 has a 2-wire, I2C -compatible serial interface. The part operates from a single 3 V or 5 V power supply. It is specified over the automotive temperature range of -40 C to +125 C and is housed in a 16-lead TSSOP package. More information on the AD7747 can be found in the AD7747 data sheet that is available from Analog Devices, Inc., and should be consulted in conjunction with this document when using the evaluation board.
AD7747 PART DESCRIPTION
The AD7747 is a high-resolution - capacitance-to-digital converter (CDC). The capacitance to be measured is connected directly to the device inputs. The architecture features inherent high resolution (24-bit no missing codes, 18-bit effective resolution at a 16.6 Hz data rate), high linearity ( 0.01%), and high accuracy ( 4 fF factory calibrated). The AD7747 capacitance input range is 8 pF (changing), while it can accept up to 17 pF absolute capacitance (not changing), which is compensated by an on-chip digital-to-capacitance converter (CAPDAC). The AD7747 is designed for single-ended or differential capacitive sensors with one plate connected to ground. For floating capacitive sensors, the AD7745 or AD7746 is recommended.
EVALUATION BOARD DESCRIPTION
The evaluation board interfaces to the USB port of a PC. Evaluation software is available with the evaluation board, which allows the user to easily communicate with the AD7747. Note that the AD7747 evaluation board software must be installed before connecting the AD7747 evaluation board to the PC.
FUNCTIONAL BLOCK DIAGRAM
OPTIONAL EXT. AVDD PC USER SOFTWARE ADP3303 VOLT. REG. EXT 5.0V 3.3V I2C SDA SCL RDY VIN VREF AVDD
USB
AD7747
CYPRES EZ USB
EEPROM (USB ID) AC-SHLD GND CIN1 (+) CIN1 ( )
07725-001
Figure 1.
Rev. 0
Evaluation boards are only intended for device evaluation and not for production purposes. Evaluation boards are supplied "as is" and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability or fitness for a particular purpose. No license is granted by implication or otherwise under any patents or other intellectual property by application or use of evaluation boards. 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 that may result from its use. Analog Devices reserves the right to change devices or specifications at any time without notice. Trademarks and registered trademarks are the property of their respective owners. Evaluation boards are not authorized to be used in life support devices or systems.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. www.analog.com Tel: 781.329.4700 Fax: 781.461.3113 2008 Analog Devices, Inc. All rights reserved.
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