AN2869 datasheet(36/43 Pages) STMICROELECTRONICS

Part #	AN2869

Description	Guidelines for designing touch sensing applications

PDF	43 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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Projected sensor design

AN2869

36/43

Doc ID 15298 Rev 6

4.1.3

H type sensor two layers

In this implementation, the Tx electrode forms an H, and the Rx electrode is a wire which

lies on the Tx square. There is an isolating material between them, and Tx square electrode

is hollow under the Rx electrode (see Figure 30). Obviously, this kind of touchkey is made of

two layers.

Figure 30.

Two-layer implementation

4.2

Linear sensor

An example of a linear sensor with five parcels is described in Figure 31. This kind of linear

touch sensor is fine when each parcel is about 6 mm to 10 mm and it could have N parcels.

So, for an overall length L, you can calculate the parcel number: N = L / parcel size (adjust

the parcel size to obtain N as an integer).

1/4L

1/2L

1/4L

1/8L

panel

PCB

0.2 to 0.5 mm

H sensor (cross section)

bottom

MS18986V2

AN2869 Datasheet(PDF) 36 Page - STMicroelectronics