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 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

Features and Benefits

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

Analog to Digital Converters

Data Sheets

Document	note
AD7142: Programmable Controller for Capacitance Touch Sensors Data Sheet (Rev. A)	PDF 1369 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

Product Highlight

Document	note
Leading Inside Advertorials: Providing an Edge in Capacitive Sensor Applications	PDF 85 kB

Frequently Asked Questions

Document	note

Order Information

Part Number	Package	Packing Qty	Temp Range	Price 1000+	RoHS
AD7142ACPZ-1500RL7 Production	32 ld LFCSP (5x5mm)	OTH 500	-40 to 85C	1.37	Y
AD7142ACPZ-1REEL Production	32 ld LFCSP (5x5mm)	REEL 5000	-40 to 85C	1.37	Y
AD7142ACPZ-500RL7 Production	32 ld LFCSP (5x5mm)	OTH 500	-40 to 85C	1.37	Y
AD7142ACPZ-REEL Production	32 ld LFCSP (5x5mm)	REEL 5000	-40 to 85C	1.37	Y