User Manual

The InterMeasurement can be used to reduce the power consumption. The VL53L4CD power consumption
depends of the duty cycle Timing Budget/InterMeasurement, so a high InterMeasurement allows to have a low
power consumption.
The minimum and maximum value of each timing is defined in the following table.
Table 4. Minimum and maximum range timing
Timing Min (ms) Default (ms) Max (ms)
TimingBudget 10 50 200
InterMeasurement
TimingBudget (or 0 to disable
the feature)
0 5000
3.3 Sigma and signal thresholds
Two thresholds can be used to improve accuracy or maximum ranging distance.
The sigma corresponds to the standard deviation of the returned pulse. If the computed sigma is above the
programmed value, the result status in structure 'VL53L4CD_Result_t' will be equal to 2 instead of 0. The value
can be changed using function VL53L4CD_SetSigmaThreshold(). The default value is 15 mm, minimum is 0 mm
(no threshold), and maximum is 16383 mm.
The signal corresponds to the minimal number of photons to consider a valid distance. If the computed signal
is below the programmed value, the result status in structure 'VL53L4CD_Result_t' will be equal to 1 instead of
0. The value can be changed using function VL53L4CD_SetSignalThreshold(). The default value is 1024 kcps,
minimum is 0 kcps (no threshold), and maximum is 65535 kcps.
The best accuracy can be reached using a low sigma and a high signal. But it also reduces the maximum ranging
distance. Benefits of the two thresholds are shown in the following table.
Table 5. Sigma and signal thresholds change effect
Limit Action
Effect on standard
deviation
Effect on maximum ranging
distance
Sigma threshold
Increase limit - +
Decrease limit + -
Signal threshold
Increase limit + -
Decrease limit - +
3.4 Detection thresholds and detection windows
In addition to the regular ranging capability, the sensor can be programmed to detect an object under certain
predefined criteria. If programmed condition are met, an interrupt is raised on PIN GPIO1. This mechanism allows
to trigger interrupts only in particular conditions. The available detection condition usecases include:
• Below a distance threshold
• Above a distance threshold
• Within two distance thresholds
• Outside of two distance thresholds
The thresholds can be changed using function VL53L4CD_SetDetectionThresholds(). By default there are no
thresholds programmed.
Note: The detection threshold needs to be used with InterMeasurement enabled (not equal to 0).
UM2931
Sigma and signal thresholds
UM2931 - Rev 1
page 9/15