VL6180X datasheet(22/79 Pages) STMICROELECTRONICS

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Functional description

VL6180X

22/79

DocID026171 Rev 6

return signal rate 0.5 ms after the start of every measurement. If it is below the ECE

threshold, the measurement is aborted and an ECE error is flagged.

Figure 13. Early convergence estimate (ECE)

ECE is enabled by setting bit 0 of SYSRANGE__RANGE_CHECK_ENABLES{0x02D}. If

enabled, the ECE threshold must be specified. To set the ECE threshold 20% below the

minimum convergence rate, the ECE threshold is calculated as follows:

The 16-bit ECE threshold should be written to

SYSRANGE__EARLY_CONVERGENCE_ESTIMATE{0x22}.

For example, if

SYSRANGE__MAX_CONVERGENCE_TIME{0x1c}

is set to 30 ms, the ECE threshold is 204.

If the return count is less than 204 after 0.5 ms, the measurement will be aborted.

Note:

The optimum value for the ECE threshold should be determined in the final application.

2.8.2

Range ignore

In a system with cover glass, the return signal from the glass (cross-talk) may be sufficient

to cause the system to converge and return a valid range measurement even when there is

no target present. The range ignore feature is designed to ensure that the system does not

range on the glass. (Cross-talk is described in more detail in Section 2.12.2).

The ignore threshold is enabled by setting bit 1 of

SYSRANGE__RANGE_CHECK_ENABLES{0x02D}

. If enabled, the ignore threshold must be

specified. In the follow example, the ignore threshold is set 20% above the system cross-

talk:

A range ignore error will be flagged if the return signal rate is less than the ignore threshold.

SYSRANGE__RANGE_IGNORE_VALID_HEIGHT

should be set to 255.

Note:

The optimum value for the ignore threshold should be determined in the final application.

time

Return

count

convergence threshold

. r

max.

convergence

ECE (0.5 ms)

measurement

aborted

converged

ECE

threshold

ECE threshold

80%

0,5

15360

SYSRANGE__MAX_CONVERGENCE_TIME (in ms)

----------------------------------------------------------------------------------------------------------------------------------------

SYSRANGE__RANGE_IGNORE_THRESHOLD{0x26}

cross-talk (Mcps)

120%

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