AD7143 Programmable Controller for Capacitance Touch Sensors

Data Sheet, Rev. 0, 1/07

The AD7143 is an integrated capacitance-to-digital converter (CDC) with on-chip environmental calibration for use in systems requiring a novel user input method. The AD7143 interfaces to external capacitance sensors implementing functions, such as capacitive buttons, scroll bars, and scroll wheels.

The CDC has eight inputs channeled through a switch matrix to a 16-bit, 250 kHz sigma-delta (Σ-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 software to run on the host processor.

The AD7143 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 touched. This ensures that there are no false or nonregistering touches on the external sensors due to a changing environment.

The AD7143 has an I2C-compatible serial interface and a separate VDRIVE pin for I2 serial interface operating voltages between 1.65 V and 3.6 V.

The AD7143 is available in a 16-lead, 4 mm x 4 mm LFCSP-VQ and operates 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 playersCell phones
Digital still cameras
Smart hand-held devices
Television, A/V, and remote controls
Gaming consoles

Features and Benefits

Programmable capacitance-to-digital converter
25 ms update rate (@ maximum sequence length)
Better than 1 fF resolution
8 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
I2C®-compatible serial interface
Separate VDRIVE level for serial interface
Interrupt output for host controller
16-lead, 4 mm x 4 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

Analog to Digital Converters

Data Sheets

Document	note
AD7143: Programmable Controller for Capacitance Touch Sensors Data Sheet (Rev. 0)	PDF 996 kB

Application Notes

Document	note
AN-830: Factors Affecting Sensor Response (Rev. 0)	PDF 161 kB
AN-856: AD7142 Applications Using Sensor Buttons (Rev. 0)	PDF 122 kB
AN-829: Environmental Compensation on the AD7142: The Effects of Temperature and Humidity on Capacitance Sensors (Rev. 0)	PDF 101 kB
AN-854: Sensor PCB Design Guidelines for the AD7142 and AD7143 Capacitance-to-Digital Converters (Rev. A)	PDF 582 kB
AN-929: Tuning the AD714x for CapTouch® Applications (Rev. 0)	PDF 618 kB
AN-857: Introduction to AD7142 Host Software Requirements (Rev. 0)	PDF 76 kB
AN-858: AD7142 Sensor Board In-Line Production Test Procedure (Rev. 0)	PDF 124 kB
AN-833: Using the AD7142 and a Capacitive Sensor to Develop a Single-Push Digital Shutter Button (Rev. 0)	PDF 99 kB