AD7142:  Programmable Controller for Capacitance Touch Sensors

The AD7142 and AD7142-1 are integrated capacitance-to-digital converters (CDCs) with on-chip environmental calibration for use in systems requiring a novel user input method. The AD7142 and AD7142-1 ...More

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AD7142:  Programmable Controller for Capacitance Touch Sensors

Product Description

The AD7142 and AD7142-1 are integrated capacitance-to-digital converters (CDCs) with on-chip environmental calibration for use in systems requiring a novel user input method. The AD7142 and AD7142-1 can interface to external capacitance sensors implementing functions such as capacitive buttons, scroll bars, or wheels.

The CDC has 14 inputs channeled through a switch matrix to a 16-bit, 250 kHz sigma-delta (∑-Δ) capacitance-to-digital 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 AD7142 and AD7142-1 have on-chip calibration logic to account for changes in the ambient environment. The calibration sequence is performed automatically and at continuous intervals, when the sensors are not touched. This ensures that there are no false or nonregistering touches on the external sensors due to a changing environment.

The AD7142 has an SPI-compatible serial interface, and the AD7142-1 has an I2C-compatible serial interface. Both parts have an interrupt output, as well as a general-purpose input/ output (GPIO).

The AD7142 and AD7142-1 are available in a 32-lead, 5 mm × 5 mm LFCSP_VQ and operate from a 2.6 V to 3.6 V supply. The operating current consumption is less than 1 mA, falling to 50 μA in low power mode (conversion interval of 400 ms).

Applications

  • Personal music and multimedia players
  • Cell phones
  • Digital still cameras
  • Smart hand-held devices
  • Television, A/V, and remote controls
  • Gaming consoles

Data Sheet, Rev. A, 1/07

Features

  • Programmable capacitance-to-digital converter
    36 ms update rate (@ maximum sequence length)
    Better than 1 fF resolution
    14 capacitance sensor input channels
    No external RC tuning components required
    Automatic conversion sequencer
  • On-chip automatic calibration logic
    Automatic compensation for environmental changes
    Automatic adaptive threshold and sensitivity levels
  • On-chip RAM to store calibration data
  • SPI®-compatible serial interface (AD7142)
  • I2C®-compatible serial interface (AD7142-1)
  • Separate VDRIVE level for serial interface
  • Interrupt output and GPIO
  • 32-lead, 5 mm x 5 mm LFCSP_VQ
  • 2.6 V to 3.6 V supply voltage
  • Low operating current
    Full power mode: less than 1 mA
    Low power mode: 50 μA

Diagrams

AD7142 Diagram
Functional Block Diagram for AD7142

Specifications

Resolution (Bits) 16bit
T-Put Rate 27.8SPS
# Chan 14
Supply V Single(+2.6 to +3.6),Single(+2.7),Single(+3),Single(+3.3)
Pwr Diss (max) 3.6mW
Sleep Pwr Diss 65µW
Ain Range ± 2 pF (Delta C)
Ref Int/Ext Int/Ext
Product Description CAPTouch (TM) Programmable Controller for 2-Electrode Capacitance Sensor with SPI or I2C Interface

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AD7156 - Ultralow Power, 1.8 V, 3 mm × 3 mm, 2-Channel Capacitance Converter

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Part# Resolution (Bits) T-Put Rate # Chan Supply V Pwr Diss (max) Input Base C (pF Max) Cin Range (pF) Pkg Type Price* (1000-4999) Product Description Interface
AD7142 16 27.8SPS 14 Single(+2.6 to +3.6), Single(+2.7), Single(+3), Single(+3.3) 3.6mW 20 ±2 CSP $1.37 CAPTouch (TM) Programmable Controller for 2-Electrode Capacitance Sensor with SPI or I2C Interface I²C/Ser 2-Wire, Ser, SPI
AD7143 16 43.5SPS 8 Single(+2.6 to +3.6) 3.6mW 20 ±2 CSP $1.25 CAPTouch (TM) Programmable Controller for 2-Electrode Capacitance Sensor with I2C Interface I²C/Ser 2-Wire, Ser
AD7147 16 111SPS 13 Single(+3), Single(+3.3) 3.6mW 20 ±8 CSP $1.30 CAPTouch (TM) Programmable Controller w/ SPI or I2C Interface for Single-Electrode Cap Sensors I²C/Ser 2-Wire, Ser, SPI
AD7148 16 4SPS 8 Multi(+3.3Anlg, +3.3Dig) 3.3mW 20 ±8 CSP $1.21 Programmable Touch Controller for Single Electrode Capacitance Sensors I²C/Ser 2-Wire, Ser
AD7150 12 100SPS 2 Single(+2.7 to +3.6) 0.43mW 10 ±4 SOP $1.37 Ultra-Lo Pwr, 2-Ch Capacitance Converter for Proximity Sensing Applications I²C/Ser 2-Wire, Ser
AD7151 12 100SPS 1 Single(+2.7 to +3.6) 0.3mW 10 ±4 SOP $1.37 Ultra-Low Power, 1-Ch, Capacitance Converter for Proximity Sensing Applications I²C/Ser 2-Wire, Ser
AD7156 12 100SPS 2 Single(+1.8), Single(+2.5), Single(+2.7), Single(+3), Single(+3.3), Single(+3.6) 306µW - - CSP $1.25 Ultralow Power, 1.8 V, 3 mm × 3 mm, 2-Channel Capacitance Converter I²C/Ser 2-Wire, Ser
AD7745 24 90SPS 1 Single(+2.7 to +5.25) 4.25mW 17 ±4 SOP $4.66 24-Bit, Cap-to-Dig Conv. w/ 1 SE/Diff Capacitive Input Ch for Interface to Dual Electrode Cap Sensor I²C/Ser 2-Wire, Ser
AD7746 24 90SPS 2 Single(+2.7 to +5.25) 4.25mW 17 ±4 SOP $5.01 24-bit, Cap-to-Dig Conv. w/ 2 SE/Diff Capacitive Input Ch for interface to Dual Electrode Cap Sensor I²C/Ser 2-Wire, Ser
AD7747 24 45.5SPS 1 Single(+2.7 to +5.25) 4.25mW 17 ±8 SOP $4.66 24-bit, Cap-to-Dig Conv w/1 SE/Diff Capacitive Input Ch for interface to Single Electrode Cap Sensor I²C/Ser 2-Wire, Ser

* The pricing listed here is provided only for budgetary purposes as recommended list price in U.S. Dollars in the United States ex factor per unit for the stated volume. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.
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