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AD7747:  24-Bit Capacitance-to-Digital Converter with Temperature Sensor

Product Details


The AD7747 is a high-resolution, Σ-Δ 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, up to 19.5-bit effective resolution), high linearity (±0.01%), and high accuracy (±10 fF factory calibrated). The AD7747 capacitance input range is ±8 pF (changing), and it can accept up to 17 pF common-mode capacitance (not changing), which can be balanced by a programmable 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 (not grounded) capacitive sensors, the AD7745 or AD7746 are recommended.

The part has an on-chip temperature sensor with a 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 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 can operate with a single power supply of 2.7 V to 5.25 V. It is specified over the automotive temperature range of −40°C to +125°C and is housed in a 16-lead TSSOP package.

Applications

Automotive, industrial, and medical systems for:

  • Pressure measurement
  • Position sensing
  • Proximity sensing
  • Level sensing
  • Flowmeters
  • Impurity detections

FEATURES and BENEFITS

  • New standard in single chip solutions
  • Interfaces to single or differential grounded sensors
  • Resolution down to 20 aF (that is, up to 19.5-bit ENOB)
  • Accuracy: 10 fF
  • Linearity: 0.01%
  • Common-mode (not changing) capacitance up to 17 pF
  • Full-scale (changing) capacitance range ±8 pF
  • Update rate: 5 Hz to 45 Hz
  • Simultaneous 50 Hz and 60 Hz rejection at 8.1 Hz update
  • Active shield for shielding sensor connection
  • Temperature sensor on-chip
    Resolution: 0.1°C, accuracy: ±2°C
  • Voltage input channel
  • Internal clock oscillator
  • 2-wire serial interface (I2C® compatible)
  • Power
    2.7 V to 5.25 V single-supply operation
    0.7 mA current consumption
  • Operating temperature: -40°C to +125°C
  • 16-lead TSSOP package

Functional Block Diagram for AD7747

Documentation

Title Content Type File Type
AD7747: 24-Bit Capacitance-to-Digital Converter with Temperature Sensor Data Sheet (Rev 0, 02/2007) (pdf, 421 kB) Data Sheets PDF
AN-1301: Using CDCs to Control Motion for Sample Aspiration  (pdf, 169 kB) Application Notes PDF
Webcast: Design And Develop Innovative And Robust Touch Sensor Interfaces Using Capacitive-To-Digital Converters
This Webcast will focus on the design and development of CDC-based touch sensors and their application, cite CDC product examples such as the AD7142, and explore development tools provided by ADI.
Webcasts WEBCAST
Boost Precision and Accuracy with Single Chip Capacitance- and Impedance-to-Digital Converters
(Analog Dialogue, Vol. 41, August, 2007)
Analog Dialogue HTML
Capacitance Sensors for Human Interfaces to Electronic Equipment
(Analog Dialogue, Vol. 40, October, 2006)
Analog Dialogue HTML
MS-2210: Designing Power Supplies for High Speed ADC  (pdf, 327 kB) Technical Articles PDF
Capacitance Sensors for Human Interfaces to Electronic Equipment
(Analog Dialogue, Vol. 40, October, 2006)
Technical Articles HTML
ADI Rolls Out Single-chip Converters for Precise Capacitance and Impedance Measurements
(Automotive Design Line, 3/4/2005)
Product Reviews HTML
Capacitance And Impedance Converters—A High-Precision “First”
(Electronic Design Europe, 4/2005)
Product Reviews HTML
ADI Rolls Out Single-Chip Converters for Precise Capacitance and Impedance Measurements
(eeProductCenter, 3/2005)
Product Reviews HTML
Motion Sensing Devices Make Integrated Systems Easy
(Electropages, 11/24/2006)
Product Reviews HTML
2008 Medical Solution Profile  (pdf, 126 kB)
High Performance ICs for Medical Imaging, Patient Monitoring, and Instrumentation
Overview PDF
AD7150 Capacitance Converter for Proximity Sensing  (pdf, 1907 kB) Overview PDF
Leading Inside Advertorials: Providing an Edge in Capacitive Sensor Applications  (pdf, 85 kB) Overview PDF
Leading Inside Advertorials: Boost Precision and Accuracy with Single Chip Capacitance- and Impedance-to-Digital Converters  (pdf, 482 kB) Overview PDF
What are Capacitive Sensors and how are they used? FAQs/RAQs HTML
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

Design Tools,Models,Drivers & Software

Title Content Type File Type
AD7746 - Microcontroller No-OS Driver Device Drivers HTML
AD7746 IIO Capacitance to Digital Converter Linux Driver Device Drivers HTML

Evaluation Kits & Symbols & Footprints

Evaluation Boards & KitsView the Evaluation Boards and Kits page for documentation and purchasing

Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.

SampleSample & Buy

Price, packaging, availability

AD7747 Model Options
Model Package Pins Temp.
Range
Packing,
Qty
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
AD7747ARUZ Status: Production 16 ld TSSOP 16 Ind Tube, 96 $5.46 $4.66 Y  Material Info PCN Purchase Sample
AD7747ARUZ-REEL Status: Production 16 ld TSSOP 16 Ind Reel, 2500 - $4.66 Y  Material Info PCN Purchase
AD7747ARUZ-REEL7 Status: Production 16 ld TSSOP 16 Ind Reel, 1000 - $4.66 Y  Material Info PCN Purchase
Price Table Help

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

AD7747 Evaluation Kit
Model Description Price RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
EVAL-AD7747EBZ Status: Production Evaluation Board $59.00 Yes -

Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.

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