Programmable Controller for
Capacitance Touch Sensors
AD7142
Rev. A
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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)
I
2
C®-compatible serial interface (AD7142-1)
Separate V
DRIVE
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
FUNCTIONAL BLOCK DIAGRAM
TEST
V
REF+
V
REF–
SDO/
SDA
SDI/
ADD0
SCLK
CS/
ADD1
INT
C
SHIELD
SRC
SRC
V
DRIVE
SWITCH
MATRIX
16-BIT
Σ-Δ
CDC
CALIBRATION
ENGINE
CONTROL
AND
DATA
REGISTERS
CALIBRATION
RAM
250kHz
EXCITATION
SOURCE
SERIAL INTERFACE
AND CONTROL LOGIC
INTERRUPT
AND GPIO
LOGIC
POWER-ON
RESET
LOGIC
AV
CC
AGND
DGND1
DGND2
DV
CC
GPIO
19
18
17
14
13
272829
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
12
15
16
20
21
22 23 24 25
26
05702-001
Figure 1.
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 (∑-∆) 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.
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 I
2
C-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).
Verzeichnis
- ・ Konfiguration des Pinbelegungsdiagramms on Seite 10
- ・ Abmessungen des Paketumrisses on Seite 37 Seite 70
- ・ Paket-Footprint-Pad-Layout on Seite 37
- ・ Teilenummerierungssystem on Seite 70
- ・ Blockdiagramm on Seite 1
- ・ Typisches Anwendungsschaltbild on Seite 39
- ・ Beschreibung der Funktionen on Seite 1 Seite 10
- ・ Technische Daten on Seite 1 Seite 5 Seite 7 Seite 8 Seite 9
- ・ Anwendungsbereich on Seite 1
- ・ Elektrische Spezifikation on Seite 11
