Programmable Controller for
Capacitance Touch Sensors
Data Sheet
AD7142
FEATURES
FUNCTIONAL BLOCK DIAGRAM
V
V
REF– REF+
29 28
TEST
27
Programmable capacitance-to-digital converter
36 ms update rate (at 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
30
31
32
1
CIN0
CIN1
CIN2
CIN3
CIN4
CIN5
CIN6
CIN7
CIN8
CIN9
CIN10
CIN11
CIN12
CIN13
POWER-ON
RESET
LOGIC
AV
CC
13
14
2
3
AGND
4
16-BIT
CALIBRATION
ENGINE
Σ-Δ
5
CDC
6
17
18
19
DV
CC
7
8
CALIBRATION
RAM
DGND1
DGND2
9
10
11
CONTROL
AND
DATA
REGISTERS
C
12
15
16
SHIELD
SRC
250kHz
EXCITATION
SOURCE
32-lead, 5 mm x 5 mm LFCSP
2.6 V to 3.6 V supply voltage
SRC
Low operating current
Full power mode: less than 1 mA
INTERRUPT
AND GPIO
LOGIC
SERIAL INTERFACE
AND CONTROL LOGIC
V
DRIVE 20
26
GPIO
Low power mode: 50 µA
22
23
24
25
21
SDO/
SDA
SDI/
ADD0
CS/
ADD1
SCLK
INT
APPLICATIONS
Figure 1.
Personal music and multimedia players
Cell phones
Digital still cameras
Smart hand-held devices
Television, A/V, and remote controls
Gaming consoles
GENERAL DESCRIPTION
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 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 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 CDC has 14 inputs channeled through a switch matrix to a
16-bit, 250 kHz sigma-delta (∑-∆) 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 are available in a 32-lead, 5 mm ×
5 mm LFCSP 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).
Rev. B
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rightsof third parties that may result fromits use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks andregisteredtrademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2006–2017 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com