Part # Application Notes Mobile Mobile Communications Communications Communications And Networking Computer And Peripherals Consumer Di datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: S-Touch™ PCB and layout guidelines


Part Details:

AN2733 S-TouchTM PCB and layout guidelines Introduction The aim of this application note is to provide guidelines for the construction and the layout of different types of printed circuit boards (PCB) for the implementation of S-TouchTM capacitive devices: the FR4 and flexible PCBs or the ITO panel. Various substrate materials are available for different PCB design construction. Among the substrate materials currently available in the market, the FR4 is the most common. FR4 is a glass fiber epoxy laminate and the PCBs can have one or several layers. Given a limited size of the touch module, the 1-layer PCB implementation is not always possible, whereas the four-layer and the 2-layer PCB are more common. For applications requiring a very compact form factor, the flexible PCB can be used. The capacitive touch module on top of the display unit requires a transparent sensor electrode and traces which can be implemented using an indium tin oxide (ITO) layer on glass/plastic panel. June 2008 Rev 1 1/24 www.st.com Contents AN2733 Contents 1 PCB design and layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Single layer PCB construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1.1 1-layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1.2 Design rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 2-layer PCB construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2.1 Design rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.3 4-layer PCB construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.3.1 Design rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.3.2 Ground polygons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.4 Flex PCB construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.5 ITO PCB construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2 Sensor s basic function description and guidelines . . . . . . . . . . . . . . 17 2.1 Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.2 Slider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.3 Rotator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.4 Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.4.1 Matrix keypad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.4.2 Matrix touchpad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3 Other considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4


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