IC-MQ Datasheet, PDF (22/39 Pages) IC-Haus GmbH – PROGRAMMABLE 9-BIT Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

iC-MQ PROGRAMMABLE 9-BIT
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev D4, Page 22/39
Offset Calibration CH1, CH2
In order to calibrate the offset the reference source
must first be selected using VOS12. Two fixed voltages
and two dependent sources are available for this pur-
pose. The fixed voltage sources should be selected for
external sensors which provide stable, self-regulating
signals.
So that photosensors can be operated in optical en-
coders iC-MQ tracks changes in offset voltages via
the signal-dependent source VDC when used in con-
junction with the controlled sensor current source for
LED supply (pin ACO). The VDC potential automati-
cally tracks higher DC photocurrents. To this end inter-
mediate potentials VDC1 and VDC2 must be adjusted
to a minimal AC ripple using the selectable k factor
(this calibration must be repeated when the gain set-
ting is altered). The ideal DC voltage level of 0.125 V
to 0.25 V is selected via input resistor Rui().
The feedback of pin voltage V(ACO) fulfills the same
task as source VDC when MR bridge sensors are sup-
plied by the controlled sensor current source. In this
instance the VDC sources do not need adjusting.
VOS12
Code
0x0
0x1
0x2
0x3
Adr 0x0E, bit 5:4
Source
0.05 · V(ACO)
0.5 V
0.25 V
VDC (VDC1 for CH1, VDC2 for CH2)
Table 26: Offset Reference Source CH1, CH2
VDC1
VDC2
Code
0x00
0x01
...
0x3F
Adr 0x07, bit 4:0; Adr 0x06, bit 7
Adr 0x08, bit 6:1
VDC = k · VPi + (1 − k) · VNi
k = 0.33
k = 0.335
k = 0.33 + VDCi · 0.0052
k = 0.66
The offset calibration range for CH1 and CH2 is de-
pendent on the selected VOS12 source and is set us-
ing OR1 and OR2. Both sine and cosine signals are
then calibrated using factors OF1 and OF2. The cal-
ibration target is reached when the DC fraction of the
differential signals PCHi versus NCHi is zero.
OR1
OR2
Code
0x0
0x1
0x2
0x3
Adr 0x09, bit 0; Adr 0x08, bit 7
Adr 0x0A, bit 5:4
Range
x1
x2
x6
x12
Table 28: Offset Range CH1, CH2
OF1
OF2
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
0x80
0
0.0079
0x81
−0.0079
0.0079 · OFi
...
−0.0079 · OFi
1
0xFF
−1
Table 29: Offset Factors CH1, CH2
Phase Correction CH1 vs. CH2
The phase shift between CH1 and CH2 can be ad-
justed using parameter PH12. Following phase cal-
ibration other calibration parameters may have to be
adjusted again (those as amplitude compensation, in-
termediate potentials and offset voltages).
PH12
Code
0x00
0x01
...
0x1F
Adr 0xD, bit 2:0; Adr 0xC, bit 7:5
Correction angle Code
Correction angle
+0
0x20
−0
+0.65
0x21
−0.65
+0.65 · PH12 ...
−0.65 · PH12
+20.2
0x3F
−20.2
Table 27: Intermediate Voltages CH1, CH2
Table 30: Phase Correction CH1 vs. CH2