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AD7148:  CapTouch™ Programmable Controller for Single-Electrode Capacitance Sensors

Product Details


The AD7148 CapTouch™ Programmable Controller is designed for use with capacitance sensors implementing functions such as buttons, scroll bars, and wheels. The sensors need only one PCB layer, enabling ultra thin applications.

The AD7148 is an integrated capacitance-to-digital converter (CDC) with on-chip environmental calibration. The CDC has 8 inputs channeled through a switch matrix to a 16-bit, 250 kHz sigma-delta (Σ-Δ) converter. The CDC is capable of sensing changes in the capacitance of the external sensors and uses this information to register a sensor activation. The external sensors can be arranged as a series of buttons, as a scroll bar or wheel, or as a combination of sensor types. By programming the registers, the user has full control over the CDC setup.

High resolution sensors require minor software to run on the host processor.

The AD7148 is designed for single electrode capacitance sensors (grounded sensors.) There is an active shield output to minimize noise pick-up in the sensor. For floating, or two electrode sensors, use the AD7143.

The AD7148 has on-chip calibration logic to account for changes in the ambient environment. The calibration sequence is performed automatically and at continuous intervals, while the sensors are not active. This ensures that there are no false or non-registering touches on the external sensors due to a changing environment.

The AD7148 has an I2C-compatible serial interface, as well as interrupt output. There is a VDRIVE pin to set the voltage level for the serial interface independently from VCC.

The AD7148 is available in a 16-lead, 4 mm × 4 mm LFCSP and operates from a 2.6 V to 3.6 V supply. The operating current consumption in low power mode is typically 26 μA.

Applications

  • Cell Phones
  • Personal Music and Multimedia Players
  • Smart Hand-held Devices
  • Television, A/V and Remote Controls
  • Gaming Consoles
  • Digital Still Cameras

FEATURES and BENEFITS

  • Programmable capacitance to digital converter
    Femto Farad resolution
    8 capacitance sensor inputs
    25ms update rate, all 8 sensor inputs
    No external RC components required
    Automatic conversion sequencer
  • On-chip automatic calibration logic
    Automatic compensation for environmental changes
    Automatic adaptive threshold and sensitivity levels
    Register map compatible with AD7143
  • On-chip RAM to store calibration data
  • I2C®-compatible serial interface
  • Separate VDRIVE level for serial interface
  • Interrupt Output
  • 16-lead, 4 mm x 4 mm LFCSP_VQ
  • 2.6 to 3.3V supply voltage
  • Low operating current
    Full power mode: 1 mA
    Low power mode: 21.5 µA

Functional Block Diagram for AD7148

OF NOTE ...

Documentation

Title Content Type File Type
AD7148: Programmable Touch Controller for Single Electrode Capacitance Sensors Data Sheet (Rev A, 01/2010) (pdf, 1236 kB) Data Sheets PDF
AN-925: Sensors for the AD7147 and AD7148 CapTouch® Controllers  (pdf, 189 kB) Application Notes PDF
AN-957: Layout Guidelines for the AD7147 and AD7148 CapTouch® Controllers  (pdf, 337 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
MS-2210: Designing Power Supplies for High Speed ADC  (pdf, 327 kB) Technical Articles PDF
2008 Medical Solution Profile  (pdf, 126 kB)
High Performance ICs for Medical Imaging, Patient Monitoring, and Instrumentation
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
AD714X Input CapTouch® Programmable Controller Linux Driver Device Drivers HTML
CapTouch Software License Agreement  (pdf, 15 kB)
Dowloading and opening the software implies acceptance of the Analog Devices software license agreement
Software Modules PDF

Evaluation Kits & Symbols & Footprints

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

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.


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