QST104 datasheet(28/45 Pages) STMICROELECTRONICS

Part #	QST104

Description	Capacitive touch sensor device 4 keys with individual key state outputs or I2C interface

PDF	45 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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Design guidelines

QST104

28/45

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 CS. Under heavy delta-CX loading of one key, cross coupling to another key’s trace can

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-CX are expected, for example when an electrode is directly touched. This is not a

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.

QST104 Datasheet(PDF) 28 Page - STMicroelectronics