DocID17613 Rev 3

9/15

AN3236

Touchkey matrix

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3

Touchkey matrix

In some applications, adding one touchkey by electrode pairs is not enough and building an

electrode network to get a touchkey matrix is more efficient.

3.1

Matrix hardware implementation

The double-ended electrode solution can be extended to create an electrode network as

shown in Figure 4: Matrix hardware implementation example

Figure 4. Matrix hardware implementation example

In this implementation example, seven channels provide a touchkey matrix of12 touchkeys.

Each touchkey is generated by interlacing a channel row with a channel column. For

example, touchkey 1 is generated by interlacing Ch1 with Ch4. It is recommended to have

homogenous sized touchkeys so that each touchkey has the same sensitivity. This

simplifies the threshold setup and acquisition can be achieved using the same sampling

capacitor value.