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PDF AT42QT2120 Data sheet ( Hoja de datos )
| Número de pieza | AT42QT2120 | |
| Descripción | QTouch 12-channel Touch Sensor IC | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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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 I2C interface
– Standalone mode – settings are fixed
• Interface:
– I2C 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 page  
AT42QT2120
1.2.2
20-pin VQFN
Table 1-2.
Pin
1
2
3
4
5
Pin Listings (20-pin VQFN)
Name
(Comms)
Name
(Standalone)
Type
KEY6/
GPO4
KEY6
I/O
KEY5/
GPO3
KEY5
I/O
KEY4/
GPO2
KEY4
I/O
KEY3/
GPO1
KEY3
I/O
KEY2/
GPO0
KEY2
I/O
6
KEY1
GUARD
I/O
7
KEY0
PROX
I/O
8 VSS
9 VDD
VSS
VDD
P
P
10 MODE MODE
I
11 SDA
N/C OD
12 RESET RESET
I
13
N/C
PXOUT
OD
14 SCL
N/C OD
15 CHANGE
16
KEY11/
GPO9
17
KEY10/
GPO8
18
KEY9/
GPO7
19
KEY8/
GPO6
20
KEY7/
GPO5
N/C
OUT6
OUT5
OUT4
OUT3
OUT2
OD
I/O
I/O
I/O
I/O
I/O
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
If Unused...
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
Leave open
Leave open
I Input only
I/O Input and output
OD Open drain output
P Ground or power O Output only
9634E–AT42–06/12
5
5 Page 
AT42QT2120
2.9 Calibration
Writing a nonzero value to the calibration byte can force a recalibration at any time. This can be
useful to clear out a stuck key condition after a prolonged period of uninterrupted detection. A
calibration command executes 15 burst cycles at LPM 1 and sets the CALIBRATE bit of the
Detection Status register during the calibration sequence.
Note: A calibration command should be sent whenever Key Control bit 0 (EN) is changed.
This changes the use of the key from a standard touch key to an output pin and
vice-versa.
2.10
Guard Channel
A guard channel to help prevent false detection is available in both modes. This is fixed on key 1
for standalone mode and programmable for comms mode by setting Key Control bit 4 (GUARD)
(see Section 5.17 on page 26).
Guard channel keys should be more sensitive than the other keys and physically bigger.
Because the guard channel key is physically bigger it becomes more susceptible to noise so it
should have a higher Oversampling (see Section 5.18 on page 27) than the other keys. In
standalone mode it is assigned to key 1 and cannot be changed.
In comms mode any key can be selected to be a guard key by setting Key Control bit 4
(GUARD).
The guard channel is connected to a sensor pad which detects the presence of touch. Because
of its larger size and sensitivity it goes into touch before the keys it surrounds (if, for example, a
hand covers all the keys).
Figure 2-1. Guard Channel Example
Guard channel
2.11 Signal Processing
2.11.1
Detect Threshold
The device detects a touch when the signal has crossed a threshold level and remained there
for a specified number of counts (see Section 5.11 on page 24). This can be altered on a
key-by-key basis using the key Detect Threshold I2C-compatible commands.
This detect threshold is based on the reference value of the particular key. The delta of the key
is obtained by subtracting the reference value from the signal value (the signal value rises when
touch is present).
9634E–AT42–06/12
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet AT42QT2120.PDF ] | |
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