QT60248C-ASG Atmel, QT60248C-ASG Datasheet - Page 40

• Manufacturer Part Number: QT60248C-ASG
• Description: IC TOUCH SENSOR 24KEY 32TQFP
• Manufacturer: Atmel
• Series: QMatrix™, QProx™r
• Type: Capacitiver

Specifications of QT60248C-ASG

• Number Of Inputs/keys: 24 Key
• Resolution (bits): 9, 11 b
• Data Interface: Serial, SPI™
• Voltage - Supply: 3 V ~ 5 V
• Current - Supply: 25mA
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFP, 32-VQFP
• Output Type: *
• Interface: *
• Input Type: *
• For Use With: 427-1087 - BOARD EVAL QT60248-AS QMATRIX
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

10620D–AT42–04/09
Mutual-capacitance Zero-dimensional Sensors
4.2.4.3
4-8
Avoiding False Key Detection
To avoid false keys, use any of the following tricks:




In addition, keep to the following general guidelines:



1. Watch out for time constants.
2. Behind from the point of view of touch.
Figure 4-9.a. 90° Crossing (Best)
Figure 4-9.c. X Under Ground Trace
Cross the X and Y traces as little as possible and then only at 90° (see
If the X and Y traces must run parallel to each other for a distance, separate the traces with a ground
trace. Where possible, use a ground trace that is twice as wide as the track-to-track gap 
(see
Consider routing the X traces behind ground planes
traces is minimized, even if the Y traces run close to the X traces adjacent to the ground flood 
(see
Route the Y traces completely behind
so they do not interact (see
Keep the X and Y traces thin where possible.
Route the Y traces farthest from touch where possible.
Generally, keep all the X traces together and all the Y traces together. This way the number of
potential false keys is substantially reduced.
Figure
Figure
Gaps are much bigger than a touch
Y
4-9.b).
4-9.c).
Y
X
X
Panel
Ground
Figure
Substrate
4-9.d).
(2)
the X traces if needed, or route the X and Y traces well apart
Figure 4-9.b. Separating ground Trace
Figure 4-9.d. Y Under X
(1)
. This means that the field between the X and Y
Y
Ground
Y
Figure
Touch Sensors Design Guide
Note:
Avoid long runs!
X
X
4-9.a).