CapTouch™ Programmable Controller for
Single-Electrode Capacitance Sensors
Programmable capacitance-to-digital converter (CDC)
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 AD7142
On-chip RAM to store calibration data
serial interface (AD7147)
I2C-compatible serial interface (AD7147-1)
Separate VDRIVE level for serial interface
Interrupt output and general-purpose input/output (GPIO)
24-lead, 4 mm × 4 mm LFCSP
2.6 V to 3.3 V supply voltage
Low operating current
Full power mode: 1 mA
Low power mode: 21.5 μA
Personal music and multimedia players
Smart handheld devices
Television, A/V, and remote controls
Digital still cameras
The AD7147 is designed for use with capacitance sensors
implementing functions such as buttons, scroll bars, and
wheels. The sensors need only one PCB layer, enabling ultra
The AD7147 is an integrated CDC with on-chip environmental
calibration. The CDC has 13 inputs channeled through a switch
matrix to a 16-bit, 250 kHz sigma-delta (∑-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
High resolution sensors require minor software to run on the
FUNCTIONAL BLOCK DIAGRAM
AND CONTROL LOGIC
13 14 15 16
SDO/ SDI/ SCLK CS/
Figure 1. AD7147 Block Diagram
The AD7147 is designed for single-electrode capacitance
sensors (grounded sensors). There is an active shield output to
minimize noise pickup in the sensor.
The AD7147 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 AD7147 has an SPI-compatible serial interface, and the
AD7147-1 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 AD7147 is available in a 24-lead, 4 mm × 4 mm LFCSP and
operates from a 2.6 V to 3.6 V supply. The operating current con-
sumption in low power mode is typically 26 μA for 13 sensors.
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rights of third parties that may result from its use. Specifications subject to change without notice. No
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