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IC-MG Datasheet, PDF (14/20 Pages) IC-Haus GmbH – 8-Bit Sin/Cos INTERPOLATION IC WITH RS422 DRIVER | |||
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iC-MG
preliminary
8-Bit Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev C1, Page 14/20
S/C Offset Calibration
To calibrate the offset the reference source must ï¬rst
be selected using VOSSC. Two ï¬xed voltages and two
dependent sources are available for this purpose. The
ï¬xed voltage sources should be selected for external
sensors which already provide stable, self-regulating
signals.
For the operation of photosensors in optical encoders,
iC-MG tracks changes in offset voltages via the signal-
dependent source VDC when used in conjunction with
the controlled power supply output supplying the en-
coder LED (pin PWR). The VDC potential automati-
cally tracks higher DC photocurrents. To this end inter-
mediate potentials VDCS and VDCC must be adjusted
to a minimal AC ripple using the selectable k factor (this
calibration must be repeated when the gain setting is
altered). The ideal DC voltage level of 0.25 V to 0.5 V
is selected via the input resistor Rui().
The feedback of pin voltage V(PWR) fulï¬lls the same
task as source VDC when MR bridge sensors are sup-
plied by the controlled power supply output. In this in-
stance the VDC sources do not need adjusting.
VOSSC
Code
0x0
0x1
0x2
0x3
Adr 0x0E, bit 5:4
Type of source
0.05 · V(PWR)
0.5 V
0.25 V
VDC (ie. VDCS, VDCC)
Table 13: S/C-Channel Offset Reference Source
VDCS
VDCC
Code
0x00
0x01
...
0x3F
Adr 0x07, bit 4:0; Adr 0x06, bit 7
Adr 0x08, bit 6:1
VDC = k · V (P â In) + (1 â k ) · V (N â In)
k = 0.33
k = 0.335
...
k = 0.66
The calibration range for the S/C offset is dependent
on the selected VOSSC source and is set using ORS
and ORC. Both sine and cosine signals are then cali-
brated using factors OFS and OFC. The calibration tar-
get is reached when the DC fraction of the differential
signals PCHx versus NCHx is zero.
ORS
ORC
Code
00
01
10
11
Adr 0x09, bit 0; Adr 0x08, bit 7
Adr 0x0A, bit 5:4
Range
x2
x4
x12
x24
Table 15: S/C-Channel Offset Range
OFS
OFC
Code
0x00
0x01
...
0x7F
Adr 0xA, bit 3:0; Adr 0x9, bit 7:4
Adr 0xC, bit 0; Adr 0xB, bit 7:1
Factor
Code
Factor
0
0x00
0
0.0079
0x01
-0.0079
...
...
...
1
0xFF
-1
Table 16: S/C-Channel Offset Factors
S/C Phase Correction
If the phase shift between the sine and cosine signal
deviates from the ideal 90° this can be compensated
for using parameter PHSC. Following this the calibra-
tion of the amplitude compensation, intermediate po-
tentials and offset voltages may have to be corrected.
PHSC
Code
0x00
0x01
...
0x1F
Adr 0xD, bit 2:0; Adr 0xC, bit 7:5
Correction angle Code
Correction angle
+0°
0x20
-0°
+ 0.63 °
0x21
- 0.63 °
...
...
...
+ 20.2 °
0x3F
- 20.2 °
Table 14: S/C-Channel Intermediate Voltages
Table 17: Phase Correction
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