IC-MN Datasheet, PDF (24/59 Pages) IC-Haus GmbH – 25-BIT NONIUS ENCODER WITH 3-CH. SAMPLING 13-BIT Sin/D INTERPOLATION

iC-MN 25-BIT NONIUS ENCODER
WITH 3-CH. SAMPLING 13-BIT Sin/D INTERPOLATION
Rev D1, Page 24/59
Gain Adjustment
The gain is set in three stages. The gain range
is first determined for sine and cosine using register
GR_x (2:0). Register GFC_x (4:0) can then be used
to finely adjust the gain of the cosine track. In the
final stage of the process the amplitude of the sine
track is adapted to suit the cosine track using regis-
ter GFS_x (10:0). With differential input signals the
overall sine gain of one track is thus calculated as
GAINS_x = GR_x * GFS_x; the total cosine gain is then
GAINC_x = GR_x * GFC_x.
Offset Calibration
When calibrating the offset the offset reference source
must first be selected using REFVOS (1:0). This set-
ting is valid for all three tracks. If VDC is selected
as the offset reference SVDCx is the reference for the
sine track and CVDCx for the cosine. The VDC refer-
ence enables the offset calibration to be automatically
tracked dependent on the DC level of the input signal.
If ACO is chosen as the offset reference the voltage at
pin ACOx, divided into ¹/₂₀, acts as a reference. This
enables the offset to be calibrated dependent on the
supply voltage of the sensor.
GR_M
GR_S
GR_N
Code
0
1
2
3
4
5
6
7
Addr. 0x00; bit 2:0
Addr. 0x10; bit 2:0
Addr. 0x20; bit 2:0
Coarse gain
6.0
12.4
16.2
20.2
26.0
31.6
39.5
48.0
Table 16: Gain range sine/cosine
GFC_M
GFC_S
GFC_N
Code k
0x00
0x01
0x02
...
0x1F
Addr. 0x00; bit 7:3
Addr. 0x10; bit 7:3
Addr. 0x20; bit 7:3
k
Fine gain GFC = 6.25 31
1
1.07
1.13
...
6.25
Table 17: Gain factor cosine
GFS_M
GFS_S
GFS_N
Code k
0x000
0x001
0x002
...
0x7FF
Addr. 0x02; bit 2:0
Addr. 0x01; bit 7:0
Addr. 0x12; bit 2:0
Addr. 0x11; bit 7:0
Addr. 0x22; bit 2:0
Addr. 0x21; bit 7:0
k
Fine gain GFS = 6.25 1984
1
1.0009
1.0018
...
6.6245
Table 18: Gain factor sine
Figure 9: Principle offset calibration circuit with se-
lectable reference sources.
REFVOS
Code
0
1
2
3
Addr. 0x0A; bit 5:4
Type of source
Feedback of pin ACO REFVOS = V(ACOx)/20
Reference V05
REFVOS = 0.5 V
Reference V025
REFVOS = 0.25 V
Tracked source VDC
REFVOS = SVDCx,
CVDCx
Table 19: Offset reference source
Source VDC is to be used as reference for current
inputs. The average potentials of sine (SVDCx) and
cosine (CVDCx) are determined by:
SVDCx = (1 − k_s) · V (PSi) + k_s · V (NSi)