AN4038 datasheet(21/39 Pages) STMICROELECTRONICS

部件名	AN4038

功能描述	Guidelines to optimize proximity detection with STM8TL5xxx capacitive sensors

PDF	39 Pages

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制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

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21 / 39 page

AN4038

Proximity sensor design

Doc ID 022686 Rev 1

21/39

4.2

Tx/Rx electrode length influence

The Tx/Rx electrode length influences the proximity detection distance. The longer the

Tx/Rx plate length, the higher the detection distance is. Figure 18 shows the influence of the

Tx/Rx electrode length on the detection range.

Figure 18.

Detection range versus Tx/Rx electrode length

In addition, the projected capacitance between the Tx and Rx electrode increases when the

Rx/Tx electrode length increases. Regarding the projected capacitance equation (see

Equation 2 and Figure 15), the higher the front area of the two electrodes is, the higher the

capacitance is. When the projected capacitance increases the noise on the acquisition

signal decreases. Figure 19 shows the influence of the Tx/Rx electrode length on the noise

standard deviation.

Figure 19.

Noise standard deviation versus Tx/Rx electrode length

AN4038 数据表(PDF) 21 Page - STMicroelectronics