iC-LNB 18-BIT OPTO ENCODER
WITH SPI AND SER/PAR INTERFACES
Rev A1, Page 23/35
CS
SCLK
OP
OP
ADR
ADR
DATA1 DATA2
DATA1 DATA2
...
...
MOSI
MISO
8 cycles
Figure 14: Write to REGISTER (cont.)
GRAY-CODE OUTPUTS
0°
90°
180°
270°
360°
In interface mode the outputs GA, GB provide two
90° shifted digital signals with 1 PPR each (Fig-
ure 15). The signals are independent of the Flex-
Count resolution (RESSUB) or the zero position
(ZPOS), but pin DIR or register bit DIR can be
applied to invert the signal GA (code inversion).
Thereby GA and GB can be used for instance to
trigger an external multiturn to count the revolutions.
GA (MSB)
GB (MSB-1)
V10 (DA10V)
N10 (DA10N)
V9 (DA9V)
N9 (DA9N)
One revolution
Figure 15: Phase of GA, GB without code inversion
ADJUSTMENT
iC-LNB is adjusted in relation to the code disc with the Example: LNB1S 42-1024
help of an electronic alignment aid.
The scan ratio for the adjustment signal at XJD can
be derived from the maximum tilt. At a tilt angle of
1.8° photodiode DA4V is approximately 74 µm from
Tilt angle
In interface mode (EPG = 0) an EXORed signal from the ideal position; with an average radius of 19.89 mm
tracks DA4V and DA10V (differential signal of the lead- for track DA4 there is an edge shift of 0.06%. The
ing track 4 and track 10 diodes) is output at pin XJD. edge shift for photodiode DA10V is contradirectional
By tilting iC-LNB output signal XJD can be given a min- and about the same size. A spike length of t/T = 0.12%
imum spike length at 0° and 180°.
is thus accrued for a maximum tilt angle of 1.8°. If we
The falling or rising edge of signal GA (MSB bit in in- were to take half of the maximum tilt angle as a target
terface mode) marks the 0° and 180° positions.
alignment, i.e. 0.9°, the device must be aligned to a
spike length of (t/T) < 0.06%.
The maximum tilt angle tolerated by the system is stip-
ulated by the resolution and the diameter of the code
disc. Table 15 shows the allocation of the maximum tilt
to the relevant code disc.
Spike length t can be computed dependent on the
speed. Under optimum conditions the maximum spike
length is t = 0.0006 / revs per second. Due to imperfect
light levels, code disc tolerances, etc. a spike length
of about half this maximum value should be aimed for
(e.g. of less than 60 µs for a speed of 300 rpm).
Code disc
tilt angle max.
1.8°
LNB1S 42-1024
LNB4S 26-1024
1.0°
The maximum spike length must be adhered to for both
spikes (at 0° and 180°); ideally, both spikes should be
the same length.
Table 15: Maximum tilt angle referenced to the chip’s
center
ICHAUS [ IC-HAUS GMBH ]
