VL6180X datasheet(27/79 Pages) STMICROELECTRONICS

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VL6180X

Functional description

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

p2p_offset

calibration

Actual Range

cross-talk

compensation

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