AD7147_15 Datasheet, PDF (1/73 Pages) Analog Devices – CapTouch Programmable Controller for Single-Electrode Capacitance Sensors

Data Sheet
CapTouch Programmable Controller for
Single-Electrode Capacitance Sensors
AD7147
FEATURES
Programmable capacitance-to-digital converter (CDC)
Femtofarad 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 AD7142
On-chip RAM to store calibration data
SPI-compatible (serial-peripheral-interface-compatible)
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
Qualified for automotive applications
APPLICATIONS
Cell phones
Personal music and multimedia players
Smart handheld devices
Television, A/V, and remote controls
Gaming consoles
Digital still cameras
GENERAL DESCRIPTION
The AD7147 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 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
CDC setup.
High resolution sensors require minor software to run on the
host processor.
CIN0 19
CIN1 20
CIN2 21
CIN3 22
CIN4 23
CIN5 24
CIN6 1
CIN7 2
CIN8 3
CIN9 4
CIN10 5
CIN11 6
CIN12 7
FUNCTIONAL BLOCK DIAGRAM
AC_SHIELD V_CC
8
11
GND
10
BIAS
9
POWER-ON
RESET LOGIC
EXCITATION
SOURCE
AD7147/
AD7147-1
CALIBRATION
RAM
16-BIT
Σ-∆
CDC
CALIBRATION
ENGINE
CONTROL
AND DATA
REGISTERS
V_DRIVE 12
SERIAL INTERFACE
AND CONTROL LOGIC
INTERRUPT
AND GPIO
LOGIC
13 14 15 16
17
SDO/ SDI/ SCLK CS/
INT
SDA ADD0
ADD1
Figure 1.
18 GPIO
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.
Rev. D
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