IC-LNB_13 Datasheet, PDF (25/35 Pages) IC-Haus GmbH – 18-BIT OPTO ENCODER WITH SPI AND SER/PAR INTERFACES

iC-LNB 18-BIT OPTO ENCODER ^preliminary
WITH SPI AND SER/PAR INTERFACES
SIGNAL CONDITIONING
Rev A1, Page 25/35
iC-LNB has various parameters for signal conditioning. ^GS
Code
0x00
Gain
0x01
The gain of the analog sine/cosine track can be set us- ^...
ing parameter GR. A gain factor of 1.33 (GR = 0x01) ^0x3F
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
The PSIN and NSIN offsets can be calibrated sep-
arately 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 cali-
brated to the calibrated offset of signal PSIN.
Table 17: Gain range for the sine/cosine track
OSP
Code
0x00
0x01
The sine/cosine signals can be calibrated in amplitude ^...
and offset (Figure 17). To this end the LED power con- ^0x7F
trol must be programmed to sum control (LCTYP = 1)
and the internal calibration signals switched to ana-
log outputs PSIN, NSIN, PCOS, and NCOS (TA = 0x1,
page 33).
OSN
The optical power of the LED can be adjusted to the _Code
approximate target amplitude (VPx/VNx) with parame- _0x00
ter LCSET(5:0). The amplitude and offset parameters _0x01
should be set to reasonable start values for this pur- _...
pose (see register reset values in Table 7).
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
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 33). The amplitude of signals
PSIN and NSIN can then be calibrated using parame-
ter 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 signal