Features
•
Number of Keys:
•
•
– Comms Mode: 1 to 12 keys (1 to 9 if wheel or slider option enabled)
– Standalone Mode: 1 to 5 keys
Technology:
– Patented spread-spectrum QTouchADC charge-transfer
Number of Output Lines:
– Comms Mode: Up to 10 channels can be configured as outputs (but they will
replace the keys)
– Standalone Mode: 1 to 5 channels can be configured as outputs
Key Outline Sizes:
– 5 mm x 5 mm or larger (panel thickness dependent)
Key Spacings:
– 6 mm or wider, center to center (panel thickness, human factors dependent)
Key Design:
– Single solid or ring shaped electrodes; widely different sizes and shapes possible
Proximity Electrode Design:
– Single solid electrodes; Key Design, Loop, PCB Trace - different sizes and shapes
possible
Wheel Size:
– Typically 30 mm – 50 mm diameter
Wheel Electrode Design:
– Spatially interpolated wheel up to 80 mm diameter
– Typical width of segments 12 mm
Slider Electrode Design:
– Spatially interpolated, resistorless design
– Typical length 50 mm – 100 mm, typical width 12 mm
– Can be an arc or other irregular shape
Substrates:
– FR-4, low cost CEM-1 or FR-2 PCB materials; polyamide FPCB; PET films, glass
Adjacent Metal:
– Compatible with grounded metal immediately next to keys
Layers Required:
– One; electrodes and components can be on same side
Electrode Materials:
– Etched copper, silver, carbon, indium tin oxide (ITO), PEDOT
Panel Materials:
– Plastic, glass, composites, painted surfaces (nonconductive paints)
Key Panel Thickness:
– Up to 15 mm glass (key size dependent)
– Up to 10 mm plastic (key size dependent)
Wheel/slider Panel Thickness:
– Up to 4 mm glass
– Up to 3 mm plastic
Key Sensitivity:
– Comms Mode – individually settable via simple commands over I
2
C interface
– Standalone mode – settings are fixed
Interface:
–
I
2
C slave mode (400 kHz)
– CHANGE status indication pin
Signal Processing:
– Self-calibration, Auto drift compensation, Noise filtering, Adjacent Key
Suppression
®
(AKS
®
)
Power:
– 1.8 V to 5.5 V
Packages:
– 20-pin SOIC/TSSOP RoHS compliant IC
– 20-pad VQFN RoHS compliant IC
•
•
•
•
•
•
•
QTouch
12-channel
Touch Sensor
IC
AT42QT2120
•
•
•
•
•
•
•
•
•
•
•
•
9634E–AT42–06/12
1. Pinouts and Schematics
1.1
1.1.1
Pinouts
20-pin SOIC/TSSOP – Comms Mode
KEY8/GPO6
KEY7/GPO5
KEY6/GPO4
KEY5/GPO3
KEY4/GPO2
KEY3/GPO1
KEY2/GPO0
KEY1
KEY0
VSS
1
2
3
4
5
6
7
8
9
10
20
19
18
17
KEY9/GPO7
KEY10/GPO8
KEY11/GPO9
CHANGE
SCL
N/C
RESET
SDA
MODE
VDD
QT2120
16
15
14
13
12
11
1.1.2
20-pin SOIC/TSSOP – Standalone Mode
OUT3
OUT2
KEY6
KEY5
KEY4
KEY3
KEY2
GUARD
PROX
VSS
1
2
3
4
5
6
7
8
9
10
20
19
18
17
OUT4
OUT5
OUT6
N/C
N/C
PXOUT
RESET
N/C
MODE
VDD
QT2120
16
15
14
13
12
11
2
AT42QT2120
9634E–AT42–06/12
AT42QT2120
1.1.3
20-pin VQFN – Comms Mode
KEY10/GPO8
17
20
KEY6/GPO4
KEY5/GPO3
KEY4/GPO2
KEY3/GPO1
KEY2/GPO0
1
2
3
4
5
18
19
16
15
14
KEY11/GPO9
KEY7/GPO5
KEY8/GPO6
KEY9/GPO7
CHANGE
SCL
N/C
RESET
SDA
QT2120
13
12
11
1.1.4
20-pin VQFN – Standalone Mode
OUT2
OUT3
OUT4
OUT5
17
20
KEY6
KEY5
KEY4
KEY3
KEY2
1
2
3
4
5
18
19
16
15
14
OUT6
MODE
KEY1
KEY0
VDD
VSS
10
6
7
8
9
N/C
N/C
PXOUT
RESET
N/C
QT2120
13
12
11
GUARD
MODE
PROX
VDD
VSS
10
6
7
8
9
3
9634E–AT42–06/12
1.2
1.2.1
Pin Descriptions
20-pin SOIC/TSSOP
Pin Listings (20-pin SOIC/TSSOP)
Name
(Comms)
KEY8/
GPO6
KEY7/
GPO5
KEY6/
GPO4
KEY5/
GPO3
KEY4/
GPO2
KEY3/
GPO1
KEY2/
GPO0
KEY1
KEY0
VSS
VDD
MODE
SDA
RESET
N/C
SCL
CHANGE
KEY11/
GPO9
KEY10/
GPO8
KEY9/
GPO7
I
Input only
Table 1-1.
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Name
(Standalone)
OUT3
OUT2
KEY6
KEY5
KEY4
KEY3
KEY2
GUARD
PROX
VSS
VDD
MODE
N/C
RESET
PXOUT
N/C
N/C
OUT6
OUT5
OUT4
Type
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
P
P
I
OD
I
O
OD
OD
I/O
I/O
I/O
Description
Comms mode: Key 8 / General-purpose output
Standalone mode: push-pull output for key 3
Comms mode: Key 7 / General-purpose output
Standalone mode: push-pull output for key 2
Comms mode: Key 6 / General-purpose output
Standalone mode: Key 6
Comms mode: Key 5 / General-purpose output
Standalone mode: Key 5
Comms mode: Key 4 / General-purpose output
Standalone mode: Key 4
Comms mode: Key 3 / General-purpose output
Standalone mode: Key 3
Comms mode: Key/slider/wheel 2 / General-purpose output
Standalone mode: Key 2
Comms mode: Key/slider/wheel 1
Standalone mode: Guard channel
Comms mode: Key/slider/wheel 0
Standalone mode: Proximity channel
Ground
Power
Mode selection pin
Comms mode: connect to Vss
Standalone mode: connect to Vdd
Comms mode: Serial Interface Data
Standalone mode: Unused
Active low reset; has internal pull-up 60 k resistor
Comms mode: no connection
Standalone mode: open drain output for proximity channel
Comms mode: Serial Interface Clock
Standalone mode: Unused
Comms mode: Active low state change interrupt (external
pull-up resistor needed)
Standalone mode: Unused
Comms mode: Key 11 / General-purpose output
Standalone mode: push-pull output for key 6
Comms mode: Key 10 / General-purpose output
Standalone mode: push-pull output for key 5
Comms mode: Key 9 / General-purpose output
Standalone mode: push-pull output for key 4
OD Open drain output
P
Ground or power
If Unused...
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
–
–
–
Pull up to Vdd
Tie to Vdd
Leave open
Pull up to Vdd
Pull up to Vdd
Leave open
Leave open
Leave open
I/O Input and output
4
AT42QT2120
9634E–AT42–06/12
AT42QT2120
1.2.2
Table 1-2.
Pin
1
2
3
4
5
6
7
8
9
10
20-pin VQFN
Pin Listings (20-pin VQFN)
Name
(Comms)
KEY6/
GPO4
KEY5/
GPO3
KEY4/
GPO2
KEY3/
GPO1
KEY2/
GPO0
KEY1
KEY0
VSS
VDD
MODE
Name
(Standalone)
KEY6
KEY5
KEY4
KEY3
KEY2
GUARD
PROX
VSS
VDD
MODE
Type
I/O
I/O
I/O
I/O
I/O
I/O
I/O
P
P
I
Description
Comms mode: Key 6 / General-purpose output
Standalone mode: Key 6
Comms mode: Key 5 / General-purpose output
Standalone mode: Key 5
Comms mode: Key 4 / General-purpose output
Standalone mode: Key 4
Comms mode: Key 3 / General-purpose output
Standalone mode: Key 3
Comms mode: Key/slider/wheel 2 / General-purpose output
Standalone mode: Key 2
Comms mode: Key/slider/wheel 1
Standalone mode: Guard channel
Comms mode: Key/slider/wheel 0
Standalone mode: Proximity channel
Ground
Power
Mode selection pin
Comms mode: connect to Vss
Standalone mode: connect to Vdd
Comms mode: Serial Interface Data
Standalone mode: Unused
Active low reset; has internal pull-up 60 k resistor
Comms mode: no connection
Standalone mode: open drain output for proximity channel
Comms mode: Serial Interface Clock
Standalone mode: Unused
Comms mode: Active low state change interrupt (external
pull-up resistor needed)
Standalone mode: Unused
Comms mode: Key 11 / General-purpose output
Standalone mode: push-pull output for key 6
Comms mode: Key 10 / General-purpose output
Standalone mode: push-pull output for key 5
Comms mode: Key 9 / General-purpose output
Standalone mode: push-pull output for key 4
Comms mode: Key 8 / General-purpose output
Standalone mode: push-pull output for key 3
Comms mode: Key 7 / General-purpose output
Standalone mode: push-pull output for key 2
OD Open drain output
P
Ground or power
If Unused...
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
–
–
–
11
12
13
14
SDA
RESET
N/C
SCL
N/C
RESET
PXOUT
N/C
OD
I
OD
OD
Pull up to Vdd
Tie to Vdd
Leave open
Pull up to Vdd
15
CHANGE
KEY11/
GPO9
KEY10/
GPO8
KEY9/
GPO7
KEY8/
GPO6
KEY7/
GPO5
I
Input only
N/C
OD
Pull up to Vdd
16
17
18
19
20
OUT6
OUT5
OUT4
OUT3
OUT2
I/O
I/O
I/O
I/O
I/O
Leave open
Leave open
Leave open
Leave open
Leave open
O Output only
I/O Input and output
5
9634E–AT42–06/12
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