QT60168C-ASG Atmel, QT60168C-ASG Datasheet - Page 39

• Manufacturer Part Number: QT60168C-ASG
• Description: IC TOUCH SENSOR 16KEY 32TQFP
• Manufacturer: Atmel
• Series: QMatrix™, QProx™r
• Type: Capacitiver

Specifications of QT60168C-ASG

• Number Of Inputs/keys: 16 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

4.2.4
4.2.4.1
4.2.4.2
Touch Sensors Design Guide
Interconnection
X Routing
Y Routing
X routing is fairly trivial as long as RC time constant rules are observed. Nearby foreign signals that have
large kHz frequency
the charge transfer. Examples of circuits to consider include D-class amplifier signals, LCD or LED drive
signals.
X routing is not touch sensitive, and so X traces can be routed with ease on any layer of a PCB, including
the side nearest to touch. However, X routing must also take the Y routing into account.
Y routing must be more carefully considered, due to Cp build-up and the need to avoid an effect called
false key detection. Y routing is only very weakly touch sensitive, so it is good practice to run Y traces on
a layer that is far from touch.
The first factor, Cp build-up, is easily dealt with by avoiding routing Y traces over or close to ground
planes (or other power planes).
The second factor, false key detection, can occur wherever there is an interaction of the Y traces with the
X traces. Remember that anywhere where X and Y get close (less than 10 mm), and the field between
them is allowed to be influenced by touch, you have a potential key or at least a touch sensitive zone that
you do not expect (see
Figure 4-8.
1. High kHz to hundreds of kHz in particular.
Potential False Key
(1)
Potential False
Key Detection
switching transients should be routed well away from X traces as they can disturb
Figure
X Trace
4-8).
Y Trace
Mutual-capacitance Zero-dimensional Sensors
Overlying Panel
10620D–AT42–04/09
4-7