QST108 STMicroelectronics, QST108 Datasheet - Page 29

• Manufacturer Part Number: QST108
• Description: Capacitive Touch Sensor Device 8 Keys With Individual Key State Outputs Or I2c Interface
• Manufacturer: STMicroelectronics

QST108
Design guidelines
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
. Under heavy delta-C
loading of one key, cross coupling to another key’s trace can
S
X
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
are expected, for example when an electrode is directly touched. This is not a
X
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.
29/47