CapTouch Programmable Controller for
Single-Electrode Capacitance Sensors
AD7147A
FUNCTIONAL BLOCK DIAGRAM
FEATURES
AC
V
GND
BIAS
SHIELD
CC
Programmable capacitance-to-digital converter (CDC)
Femtofarad (fF) resolution
E4
D2
E2
E3
POWER-ON
RESET LOGIC
13 capacitance sensor inputs
D3
A3
B3
A4
C3
A5
B4
B5
C4
C5
D4
D5
E5
CIN0
CIN1
CIN2
CIN3
CIN4
CIN5
CIN6
CIN7
CIN8
CIN9
CIN10
CIN11
CIN12
9 ms update rate, all 13 sensor inputs
No external RC components required
Automatic conversion sequencer
EXCITATION
SOURCE
On-chip automatic calibration logic
Automatic compensation for environmental changes
Automatic adaptive threshold and sensitivity levels
Register map is compatible with the AD714x
On-chip RAM to store calibration data
Serial peripheral interface (SPI) (AD7147A)
I2C-compatible serial interface (AD7147A-1)
Separate VDRIVE level for serial interface
Interrupt output and general-purpose input/output (GPIO)
25-ball, 2.3 mm × 2.1 mm WLCSP
CALIBRATION
AD7147A
RAM
16-BIT
Σ-Δ
CDC
CALIBRATION
ENGINE
CONTROL
AND DATA
REGISTERS
2.6 V to 3.6 V supply voltage
Low operating current
B2 TP
INTERRUPT
AND GPIO
LOGIC
Full power mode: 1 mA
Low power mode: 28.96 μA
SERIAL INTERFACE
AND CONTROL LOGIC
C2
A2
GPIO
V
DRIVE
APPLICATIONS
E1
D1
SDI SCLK CS
(ADD1)
C1
B1
A1
SDO
(SDA) (ADD0)
INT
Cell phones
NOTES
Personal music and multimedia players
Smart handheld devices
Television, A/V, and remote controls
Gaming consoles
1. PIN NAMES IN PARENTHESES ARE FOR THE AD7147A-1.
Figure 1.
Digital still cameras
The AD7147A is designed for single electrode capacitance
sensors (grounded sensors). There is an active shield output to
minimize noise pickup in the sensor.
GENERAL DESCRIPTION
The AD7147A CapTouch™ 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 ultrathin applications.
The AD7147A has on-chip calibration logic to compensate for
changes in the ambient environment. The calibration sequence
is performed automatically and at continuous intervals as long
as 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 AD7147A is an integrated CDC with on-chip environmen-
tal calibration. The CDC has 13 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. By programming the registers, the user has full control
over the CDC setup.
The AD7147A has an SPI-compatible serial interface, and the
AD7147A-1 has an I2C®-compatible serial interface. Both parts
have an interrupt output, as well as a GPIO. There is a VDRIVE pin
to set the voltage level for the serial interface independent of VCC.
The AD7147A is available in a 25-ball, 2.3 mm × 2.1 mm
WLCSP and operates from a 2.6 V to 3.6 V supply. The operating
current consumption in low power mode is typically 28.96 μA
for 13 sensors.
High resolution sensors require minor software to run on the
host processor and may require two PCB layers.
Rev. B
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
rights of third parties that may result from its 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 and registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
©2009 Analog Devices, Inc. All rights reserved.
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