MPR031EP Freescale Semiconductor, MPR031EP Datasheet - Page 20

• Manufacturer Part Number: MPR031EP
• Description: Capacitance Touch Sensors PESCE DFN
• Manufacturer: Freescale Semiconductor

Specifications of MPR031EP

• Package / Case: UDFN-8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

MPR03X
20
8
8.1
The MPR03X has three levels of filtering. The first and second level filters will allow the application to condition the signal for
undesired input variation. The third level filter can be configured to reject touch stimulus and be used as a baseline for touch
detection. Each level of filtering will be further described in this section.
8.2
The first level filter is designed to filter high frequency noise by averaging samples taken over short periods of time. The number
of samples can be configured to equal a set of values ranging from 6 to 34 samples. This value is set by the FFI in the AFE
Configuration Register
the Filter Configuration Register
Note that the electrode charge time must be configured for the capacitance in the application. The resulting value will affect the
period of the first level filter.
8.3
The second level filter is designed to filter low frequency noise and reject false touches due to inconsistent data. The number of
samples can be configured to equal a set of values ranging from 4 to 18. This value is set by the SFI in the Filter Configuration
Register
(Section
Note that the ESI (Electrode Sample Interval) must be configured to accommodate the low power requirements of a system.
Thus, the resulting value will affect the period of the second level filter.
The raw data from the second level of filtering is output in the Filtered Data High and Filtered Data Low registers, as shown in
Section
8.3.1
The Filter Configuration register is used to set. The address of the Electrode Configuration Register is 0x43.
5.3.
8.3.1).
Filtering
Introduction
First Level
Second Level
(Section
Filter Configuration Register
Reset:
8.3.1). The timing of this filter is determined by the configuration of ESI in the Filter Configuration Register
W
R
(Section
7
0
7.4.1). The timing of this filter is determined by the configuration of the electrode charge time in
(Section
= Unimplemented
CDT
6
0
8.3.1).
Figure 26. Filter Configuration Register
5
0
4
0
SFI
3
0
2
0
ESI
1
0
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0
0
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