文档介绍：Touchscreen Layout
Matthew Trend
11th August 2009
1
Overview
ITO patterns + performance
1 layer patterns
2 layer patterns
Structure
1 layer options
2 layer options
Shielding
Wiring
Tracking methods and materials
Edge Shielding
Design parison
maXTouch specific design rules
Table parison between all ITO patterns
Selection flow chart to help pattern selection
Substrates
PET
Glass
Other materials
Artwork checking + testing
X resistance
2
Spreading the capacitive field
An XY touchscreen is simply 2 wide sliders at 90 degrees to each other
We need to spread the capacitive field in the same way as a 2D slider
Using area to spread the capacitive field
the distance between electrode connections has a maximum of about 16mm
Using resistive segments to spread the capacitive field.
the distance between X connections can be easily increased
The resistive method can only work using the X drive lines
3
Triangle and Bar
4
2 layer triangle and bar - pattern
5
2 layer triangle and bar - resistor divider
resistive detail
What resistance is OK?
The resistance between X connections should be more than 3K
The resistance should be more than 10x the series resistance between the IC and the electrode connection.
6
2 layer triangle and bar - crossover detail
X in front or Y in front?
X in front is more linear
Y in front allows shielding the edge X tracks
Minimise the crossover capacitance, while still keeping the Y resistance from increasing too much
7
2 layer triangle and bar – maximum resistance of Y electrode
The Y electrode has a maximum resistance it can be to plete collection of charge during the dwell period
This limits the width of the Y electrode
Calculation of the maximum resistance depends on the time constant
Calculation of the time constant to help determine X and Y bar widths:
8
2 layer triangle and bar - stack
a typical 2 layer stack
These dimensions are typical
All dimensions can be reduced if necessary
9
2 layer triangle and bar - pros and con