IC-LO Datasheet, PDF (14/21 Pages) IC-Haus GmbH – TRIANGULATION SENSOR

iC-LO
TRIANGULATION SENSOR
RECEIVED SIGNAL MONITORING
preliminary
Rev A1, Page 14/21
Two sum comparators have been integrated to mon-
itor the system and evaluate the intensity of the re-
ceived light pulse. A switching threshold can be con-
figured separately for each of the comparators. The
warning threshold is configured by using VTHSW and
an error threshold by using VTHSE. If the received
light pulse undershoots the relevant set threshold, the
corresponding comparator output (KSw and KSe, see
block diagram) is set to low. It makes sense to set
the warning threshold higher than the error threshold.
The warning threshold could indicate that the sensor
is contaminated. If the intensity of the received light
pulse undershoots the error threshold, the switching
output is deactivated as a decision cannot be safely
made (see Table 21).
THSW
Addr. 0x05; bit 4:0
RW
THSE
Addr. 0x06; bit 4:0
RW
Code
Description
0x00
VTHSx = 2.8 mV
0x01
VTHSx = 5.6 mV
..
0x1F
VTHSx = 89.6 mV
Table 17: Thresholds Sum Comparators, x = W, E
SAMPLE POINT, DIGITAL SIGNAL CONDITIONING, AND OUTPUT CONFIGURATION
The signal conditioning chain between the comparator
outputs and the switching outputs is shown in Figure 3.
Figure 3: Digital processing and signal output
FIN
Addr. 0x09; bit 3:0
RW
Code
Description
0x0
1
0x1
2
0x2
3
...
0xF
16
Table 18: Number of measurements per cycle
Digital filter
To improve noise immunity a measurement cycle (see
Figure 4), which results in an update of the switching
and warning outputs, can consist of several individual
measurements (see Figure 5). The number of individ-
ual measurements in a measurement cycle is set using
FIN. After each individual measurement the last indi-
vidual measurements set through FIN are collated to
form a measurement cycle and evaluated.
Update
switching
output
Single measurement
Measurement cycle consisting of FIN-single measurements
FIM
Addr. 0x09; bit 7:4
RW
Code
Description
0x0
1
0x1
2
0x2
3
...
0xF
16
Table 19: Number of measurements complementary
to current comparator state
Figure 4: Measurement cycle
In doing so, each comparator output (KD, KSw, and
KSe) is separately filtered. There must then be a mini-
mum number of individual measurements complemen-
tary to the current filtered comparator output (KDF,
KSwF, and KSeF) so that the corresponding filtered
comparator output changes its state. This number is
configured using FIM.
Sample point in time
The point in time at which the outputs of the three com-
parators are sampled during an individual measure-
ment (t_sample, see Figure 5) can be shifted using pa-
rameter SKO. This shift is always referenced to the ris-
ing edge of the light pulse generated in the LED driver.