AT42QT1070-MMH Atmel, AT42QT1070-MMH Datasheet - Page 22

IC TOUCH SENSOR 7KEY 20-VQFN

AT42QT1070-MMH

Manufacturer Part Number
AT42QT1070-MMH
Description
IC TOUCH SENSOR 7KEY 20-VQFN
Manufacturer
Atmel
Type
Capacitiver
Datasheets

Specifications of AT42QT1070-MMH

Number Of Inputs/keys
7 Key (Comms), 5 Key (Standalone)
Data Interface
I²C
Voltage Reference
Internal
Voltage - Supply
1.8 V ~ 5.5 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
20-VFQFN Exposed Pad
Supply Voltage
1.8 V to 5.5 V
Dimensions
3 mm L x 3 mm W x 0.8 mm H
Temperature Range
- 40 C to + 85 C
Termination Style
SMD/SMT
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Supply
-
Resolution (bits)
-
Touch Panel Interface
-
Data Rate/sampling Rate (sps, Bps)
-
Lead Free Status / Rohs Status
Lead free / RoHS Compliant

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
AT42QT1070-MMH QS529
Manufacturer:
Atmel
Quantity:
9 390
10620D–AT42–04/09
Self-capacitance Zero-dimensional Sensors
3.2.2
3-2
Electrode Shapes
An electrode is simply the patch of conductive material on the substrate that forms the sensor. Common
shapes are filled discs, squares and rectangles (see
Figure 3-2.
It is also possible to use a hatched pattern (such as a 50 percent mesh fill) for the electrode, if desired
(see
area interacting with the touch, and so there is some drop in sensitivity.
Figure 3-3.
It is a common mistake to assume that the electrode shape and the graphic key symbol on the panel
should be the same. In fact, it is often better to make the electrodes larger than the graphic especially
with small key sizes since key sensitivity falls off at the edges; an oversize electrode not only
compensates for this but also allows for off-center touch with good response. Generally, it is a good idea
to make the electrode shape extend 2–3 mm beyond the graphic symbol. Of course, this is not always
possible, for example on a densely spaced panel. As a rule, the electrode shape should have a minimum
dimension of at least 4 times the panel thickness for reliable operation.
Electrodes that are implemented by interdigitating the sensor electrode with ground
be considered a “waste” of capacitance and degrade SNR; plain and simple electrodes are almost
always better.
Figure 3-4.
Remember that with self-capacitance sensors, the sensitivity comes from the area of the electrode that
is interacting with the touching object, and nowhere else. Therefore, electrodes with exotic shapes are
not recommended (for example, long, thin electrodes or electrodes with complex “pointy” boundaries).
1. A mesh pattern may have some advantages for aesthetic or optical reasons.
Figure
3-3). This tends to reduce the natural capacitance of the key, but also equally reduces the
Common Electrode Shapes
Electrodes with 50 Percent Mesh Fills
Interdigitating Electrodes Result in a Poor SNR
Sensor
Trace
Figure
3-2).
Ground
Trace
Touch Sensors Design Guide
(Figure
3-4) can also
(1)

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