AD7142 datasheet(23/68 Pages) AD

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AD7142

Rev. 0 | Page 23 of 68

CAPACITANCE SENSOR BEHAVIOR WITH

CALIBRATION

The AD7142 on-chip adaptive calibration algorithm prevents

sensor detection errors such as the one shown in Figure 32. This

is achieved by monitoring the CDC ambient levels and

internally adjusting the initial offset level register values

according to the amount of ambient drift measured on each

sensor. This closed loop routine ensures the reliability and

repeatable operation of every sensor connected to the AD7142

under dynamic environmental conditions. Figure 33 shows a

simplified example of how the AD7142 applies the adaptive

calibration process resulting in no interrupt errors under

changing CDC ambient levels due to environmental conditions.

SENSOR 1 INT

ASSERTED

STAGE_HIGH_THRESHOLD

(POST CALIBRATED

CHANGING ENVIRONMENTAL CONDITIONS

NOTES

1. INITIAL STAGE_OFFSET_HIGH REGISTER VALUE

2. POST CALIBRATED REGISTER STAGE_HIGH_THRESHOLD

3. POST CALIBRATED REGISTER STAGE_HIGH_THRESHOLD

4. INITIAL STAGE_LOW_THRESHOLD

5. POST CALIBRATED REGISTER STAGE_LOW_THRESHOLD

6. POST CALIBRATED REGISTER STAGE_LOW_THRESHOLD

CDCAMBIENT

VALUE DRIFTING

STAGE_LOW_THRESHOLD

(POST CALIBRATED

SENSOR 2 INT

ASSERTED

Figure 33. Typical Sensor Behavior with Calibration Applied on the Data Path

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