AN4038 datasheet(22/39 Pages) STMICROELECTRONICS

Part #	AN4038

Description	Guidelines to optimize proximity detection with STM8TL5xxx capacitive sensors

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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22 / 39 page

Proximity sensor design

AN4038

22/39

Doc ID 022686 Rev 1

In conclusion, increasing the length of the proximity sensor, significantly increases detection

distance and decreases noise. It is the best compromise in term of detection distance and

noise immunity. To increase the detection distance of the proximity sensor system, it is

recommended to increase length of the Tx/Rx electrodes first before increasing the spacing

between the Tx/Rx electrodes or the electrode width.

4.3

Tx/Rx electrode width influence

The plate width also influences the detection distance. Figure 20 shows the variation of the

detection distance versus electrode width.

Figure 20.

Detection range versus Tx/Rx electrode width

The width of the Tx/Rx electrodes have a low impact on the detection distance. When the

Rx/Tx electrode width is greater than 1.5 mm, the detection distance increases very slowly

compared to that of the width. When the width is less than 1.5 mm, the detection distance

variation is very low.

AN4038 Datasheet(PDF) 22 Page - STMicroelectronics