QT114A-ISG Atmel, QT114A-ISG Datasheet - Page 39

• Manufacturer Part Number: QT114A-ISG
• Description: IC TOUCH SENSOR PROX 8SOIC
• Manufacturer: Atmel
• Series: QLevel™r
• Type: Liquid or Powderr

Specifications of QT114A-ISG

• Output Configuration: Open Collector: Dry-Low
• Mounting Type: Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Voltage Rating: 2.45 ~ 5.25 V
• Current: 20uA
• Current - Supply: *
• Output Type: *
• Interface: *
• Input Type: *
• Operating Supply Voltage: 2.5 V to 5.25 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Package / Case: -
• Lead Free Status / Rohs Status: Details

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