User manual

DocID026171 Rev 6 27/79
VL6180X Functional description
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2.12 Other system considerations
This section describes part-to-part range offset and system cross-talk. In addition, a
procedure for cross-talk calibration is given.
2.12.1 Part-to-part range offset
The VL6180X is factory calibrated to produce an absolute linear range output as shown in
Figure 16. The part-to-part range offset is calibrated during manufacture and stored in
SYSRANGE__PART_TO_PART_RANGE_OFFSET{0x24} (two’s complement).
RESULT__RANGE_RAW{0x64} reports the range with the part-to-part offset already applied.
Figure 16. Part-to-part range offset
2.12.2 Cross-talk
Cross-talk is defined as the signal return from the cover glass. The magnitude of the cross-
talk depends on the type of glass, air gap and filter material. Cross-talk results in a range
error (see Figure 17) which is proportional to the ratio of the cross-talk to the signal return
from the target. The true range is recovered by applying automatic cross-talk compensation.
Figure 17. Cross-talk compensation
To enable cross-talk compensation it is necessary to write the calibrated cross-talk value to
SYSRANGE__CROSSTALK_COMPENSATION_RATE{0x1E}in 9.7 format. A cross-talk
calibration procedure is described in Section 2.12.4.
2.12.3 Offset calibration procedure
Complete steps 1-3 to see if part-to-part offset calibration is required.
Actual Range
Measured range
p2p_offset
calibration
Actual Range
Measured range
cross-talk
compensation