IC-LNB_16 Datasheet, PDF (26/37 Pages) IC-Haus GmbH – 18-BIT OPTO ENCODER

iC-LNB 18-BIT OPTO ENCODER ^preliminary
WITH SPI AND SER/PAR INTERFACES
SIGNAL CONDITIONING
Rev B2, Page 26/37
iC-LNB has various parameters for signal conditioning. ^GS
Code
0x00
0x01
Gain
...
The gain of the analog sine/cosine track can be set _0x3F
using parameter GR. A gain factor of 1.33 (GR = 0x01)
can be used for most applications.
Addr. 0x00; bit 5:0
Gain factor
1.0
1.01
1+GS·0.0053
1−GS·0.0053
2.0
Table 18: PSIN and NSIN gain
GR
Code
00
01
10
11
Addr. 0x07; bit 1:0
Gain factor
1.0
1.33
1.6
2.0
Table 17: Gain range for the sine/cosine track
The sine/cosine signals can be calibrated in amplitude
and offset (Figure 17). To this end the LED power con-
trol must be programmed to sum control (LCTYP = 1)
and the internal calibration signals switched to analog
outputs PSIN, NSIN, PCOS, and NCOS (TA = 0x1, page
34).
The optical power of the LED can be adjusted to the
approximate target amplitude (VPx/VNx) with parame-
ter LCSET(5:0). The amplitude and offset parameters
should be set to reasonable start values for this purpose
(see register reset values in Table 7).
The PSIN and NSIN offsets can be calibrated separately
using parameters OSP and OSN. The offset of signal
PSIN must be calibrated to reference signal VDDAH.
This signal is available in test mode at pin NCOS. The
offset of signal NSIN must then be calibrated to the
calibrated offset of signal PSIN.
OSP
Code
0x00
0x01
...
0x7F
Addr. 0x02; bit 6:0
Offset values
0.45 · VDDA
0.4508 · VDDA
(0.45
+
OSP·0.1
127
)
·
VDDA
0.55 · VDDA
Table 19: PSIN offset
OSN
Code
0x00
0x01
...
0x7F
Addr. 0x03; bit 6:0
Offset values
0.45 · VDDA
0.4508 · VDDA
(0.45
+
OSN·0.1
127
)
·
VDDA
0.55 · VDDA
Table 20: NSIN offset
TA = 0x1
TMUX = 0x0D
or
TMUX = 0x0E
PSIN
NSIN
PCOS
VPx
VNx
NCOS
GNDA
VDDAH
(x = S, C)
VPx
VDDAH
VNx
Figure 17: Sine/cosine signal calibration
Cosine calibration
To calibrate the cosine signals TMUX must be pro-
grammed to 0x0E. The amplitude of signals PCOS and
NCOS can then be calibrated to the same amplitude as
that of the sine signals using parameter GS.
GC
Code
0x00
0x01
...
0x3F
Addr. 0x01; bit 5:0
Gain factors
1.0
1.01
1+GC·0.0053
1−GC·0.0053
2.0
Sine calibration
To calibrate the sine signals TMUX must be pro-
grammed to 0x0D (page 34). The amplitude of signals
PSIN and NSIN can then be calibrated using parameter
GS. The target amplitude (VPx/VNx) is 500 mVp.
Table 21: PCOS and NCOS gain
The PCOS and NCOS offsets can be calibrated sep-
arately using parameters OCP and OCN. The offset
of signal PCOS must be calibrated to reference sig-
nal VDDAH. This signal is available in test mode at