AD7142ACPZ-500RL7 Datasheet, PDF (1/73 Pages) Analog Devices – Programmable Controller for Capacitance Touch Sensors

FEATURES
Programmable capacitance-to-digital converter
36 ms update rate (@ 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
32-lead, 5 mm x 5 mm LFCSP_VQ
2.6 V to 3.6 V supply voltage
Low operating current
Full power mode: less than 1 mA
Low power mode: 50 μA
APPLICATIONS
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 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 CDC has 14 inputs channeled through a switch matrix to a
16-bit, 250 kHz sigma-delta (∑-Δ) 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.
Rev. A
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Programmable Controller for
Capacitance Touch Sensors
AD7142
CIN0 30
CIN1 31
CIN2 32
CIN3 1
CIN4 2
CIN5 3
CIN6 4
CIN7 5
CIN8 6
CIN9 7
CIN10 8
CIN11 9
CIN12 10
CIN13 11
FUNCTIONAL BLOCK DIAGRAM
V_REF– V_REF+
29
28
TEST
27
POWER-ON
RESET
LOGIC
16-BIT
Σ-Δ
CDC
CALIBRATION
ENGINE
CONTROL
AND
DATA
REGISTERS
CALIBRATION
RAM
13 AVCC
14 AGND
17 DV_CC
18 DGND1
19 DGND2
C_SHIELD 12
SRC 15
SRC ¹⁶
250kHz
EXCITATION
SOURCE
V_{DRIVE 20}
SERIAL INTERFACE
AND CONTROL LOGIC
INTERRUPT
AND GPIO
LOGIC
26 GPIO
21
22
23
24
25
SDO/ SDI/ _SCLK CS/
INT
SDA ADD0
ADD1
Figure 1.
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 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 AD7142 and AD7142-1 are available in a 32-lead, 5 mm ×
5 mm LFCSP_VQ 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).
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