STMPE1208S datasheet(14/51 Pages) STMICROELECTRONICS

Part #	STMPE1208S

Description	Xpander Logic with 12-channel touchkey

PDF	51 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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14 / 51 page

Capacitive sensors

STMPE1208S

14/51

Capacitive sensors

The STMPE1208S capacitive sensor is based on fully digital, impedance change detection

engine that is capable of detecting very small change in capacitance.

Figure 8.

Capacitive sensors

5.1

Capacitive sensing

The STMPE1208S senses a human touch by the additional capacitance introduced to the

pad (with respect to ground). This capacitance causes a delay in a clock signal on the

sensing pad, and the delay in the sensing pad is compared with a reference clock and the

difference is a direct representation of the additional capacitance introduced by the

proximity/touch of finger.

Figure 9.

Capacitive sensing

Automatic calibration

Unit

Calibration control

parameters

Data filtering

Data filtering control

Parameters

7-bit impedance value

of each channel

Touchkey

Impedance sensor

Calibrated

impedance

Touched

keys

STMPE1208S Datasheet(PDF) 14 Page - STMicroelectronics