CapTouch Programmable Controller for
Single-Electrode Capacitance Sensors
Programmable capacitance-to-digital converter (CDC)
Femtofarad (ff) resolution
13 capacitance sensor inputs
9 ms update rate, all 13 sensor inputs
No external RC components required
Automatic conversion sequencer
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
2.6 V to 3.6 V supply voltage
Low operating current
Full power mode: 1 mA
Low power mode: 28.96 μA
Personal music and multimedia players
Smart handheld devices
Television, A/V, and remote controls
Digital still cameras
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 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.
High resolution sensors require minor software to run on the
host processor and may require two PCB layers.
FUNCTIONAL BLOCK DIAGRAM
ACSHIELD VCC GND
E4 D2 E2
AND CONTROL LOGIC
E1 D1 C1 B1
SDO SDI SCLK CS
1. PIN NAMES IN PARENTHESES ARE FOR THE AD7147A-1.
The AD7147A is designed for single electrode capacitance
sensors (grounded sensors). There is an active shield output to
minimize noise pickup in the sensor.
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
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.
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
©2009 Analog Devices, Inc. All rights reserved.