AK4160 Datasheet, PDF (10/40 Pages) Asahi Kasei Microsystems – 16-channel Capacitive Touch Sensor IC

[AK4160]
■ Noise Reduction Filter
The voltage of a sense terminal is measured for N consecutive times. Then the first filter calculates the average value,
discarding the minimum and the maximum values. The N of the measurement time is user-selectable from 4, 6, 10, and
18 times. (Address 0x70 NF1S1-0 bits) The sampling rate is dependent on the charge time.
The second filter has the same structure as the first filter. The outputs of the first filter are input to the second filter. The N
of the measurement time is user-selectable from 4, 6, 10, and 18 times independent of the first filter. (Address 0x70
NF2S1-0 bits) The sampling rate of the second filter is user-selectable from 4ms to 512ms in factorial of 2 steps. (Address
0x74 TSR2-0 bits)
The output rate of the second filter is “Sampling Rate × Sample Count”. The output data is compared to “The Noncontact
Reference Value” that output by the calibration circuit for environment changes.
The Voltage of
Sense terminal
Calculation of median averaging after 6 measurement,
repeating charge and discharge.
(6 Sample Setting in the first filter)
CS0
CS1
Sampling Rate
Calculation of median averaging after 4 times acquisition
of the output data from the first filter, and updating to
result
(4 Sample Setting in the second filter)
CS0
Data
CS1
Data
Result Update
Figure 7. The Measurement of a Sense Terminal and The Data Update
MS1313-E-01
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2011/11