STMPE16M31 datasheet(50/85 Pages) STMICROELECTRONICS

Part #	STMPE16M31

Description	S-Touch® 16/24-channel touchkey controller with PWM and ratio engines

PDF	85 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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50 / 85 page

Touch sensor controller

STMPE16M31, STMPE24M31

50/85

Doc ID 16174 Rev 4

The impedance reading is the output of an internal MAF (median averaging filter). As up to

16 samples are taken for each reading, the impedance reading is the sum of 16 of 9-bit

samples.

To allow maximum consistency, the 3 impedance readings are always 13-bit, whichever

MAF setting is used.

The touch variance (TVR) and environmental variance (EVR) registers are specified in a 9-

bit format. For comparison with the impedances, the TVR and EVR would be INTERNALLY

shifted 4 bits up.

13.3

Auto-tuning

The capacitive sensor hardware in the STMPExxM31 devices has a sensitivity of 15 fF and

a range of 512 steps giving it a dynamic range of 7.5 pF. This means that at any time, the

device is able to sense a change in capacitance up to 7.5 pF. When the channel capacitance

moves out of the 7.5 pF window, the auto tuning feature kicks in to ensure proper sensing

operation.

Figure 15.

Auto-tuning operation

Obsolete

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STMPE16M31 Datasheet(PDF) 50 Page - STMicroelectronics