QST608 ST Microelectronics, QST608 Datasheet - Page 26

• Manufacturer Part Number: QST608
• Description: Capacitive touch sensor device
• Manufacturer: ST Microelectronics

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Design guidelines
5.7
26/44
It is important to limit the amount of stray capacitance on the SNS terminals, for example by
minimizing trace lengths and widths to allow for higher gain without requiring higher values
of C
cause the other key to trigger. Therefore, electrode traces from adjacent keys should not be
run close to each other over long runs in order to minimize cross-coupling if large values of
delta-C
problem when the electrodes are working through a plastic panel with normal touch
sensitivity.
For additional information on PCB layout and construction, please contact your local ST
Sales Office for a list of available application notes.
Slider and rotor layout
The QST608 can connect to either a rotor or a linear slider element
these designs is found in US Patent 4,264,903 (expired).
Figure 5.
1. Tips of triangles should be spaced ≤ 4mm apart.
The first and last positions of the linear slider have larger touch areas.
Figure 6.
SNSC_MCK1 SNSA_MCK1 SNSB_MCK1 SNSC_MCK1
S
. Under heavy delta-C
0
X
are expected, for example when an electrode is directly touched. This is not a
Slider and rotor construction
Slider layout details
Positions 0 to 127 (at 7 bits)
1 to 126
X
loading of one key, cross coupling to another key’s trace can
127
SNSB_MCK1
Position 85
SNSC_MCK1
Position 0
(Figure
5). The basis of
Position 43
SNSA_MCK1
QST608