iC-MQ PROGRAMMABLE 9-BIT
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev D4, Page 22/39
Offset Calibration CH1, CH2
The offset calibration range for CH1 and CH2 is de-
In order to calibrate the offset the reference source pendent on the selected VOS12 source and is set us-
must first be selected using VOS12. Two fixed voltages ing OR1 and OR2. Both sine and cosine signals are
and two dependent sources are available for this pur- then calibrated using factors OF1 and OF2. The cal-
pose. The fixed voltage sources should be selected for ibration target is reached when the DC fraction of the
external sensors which provide stable, self-regulating differential signals PCHi versus NCHi is zero.
signals.
OR1
OR2
Code
0x0
Adr 0x09, bit 0; Adr 0x08, bit 7
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().
Adr 0x0A, bit 5:4
Range
x1
0x1
x2
0x2
x6
0x3
x12
Table 28: Offset Range CH1, CH2
OF1
OF2
Code
0x00
0x01
...
Adr 0xA, bit 3:0; Adr 0x9, bit 7:4
Adr 0xC, bit 0; Adr 0xB, bit 7:1
Factor
Code
0x80
0x81
...
Factor
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.
0
0
0.0079
−0.0079
−0.0079 · OFi
−1
0.0079 · OFi
1
0x7F
0xFF
VOS12
Code
0x0
Adr 0x0E, bit 5:4
Table 29: Offset Factors CH1, CH2
Source
0.05 · V(ACO)
0.5 V
0x1
Phase Correction CH1 vs. CH2
0x2
0.25 V
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).
0x3
VDC (VDC1 for CH1, VDC2 for CH2)
Table 26: Offset Reference Source CH1, CH2
VDC1
Adr 0x07, bit 4:0; Adr 0x06, bit 7
Adr 0x08, bit 6:1
VDC2
Code
0x00
0x01
...
PH12
Code
0x00
0x01
...
Adr 0xD, bit 2:0; Adr 0xC, bit 7:5
VDC = k · VPi + (1 − k) · VNi
k = 0.33
Correction angle
+0
Code
0x20
0x21
...
Correction angle
−0
k = 0.335
+0.65
−0.65
k = 0.33 + VDCi · 0.0052
k = 0.66
+0.65 · PH12
+20.2
−0.65 · PH12
−20.2
0x3F
0x1F
0x3F
Table 27: Intermediate Voltages CH1, CH2
Table 30: Phase Correction CH1 vs. CH2
ICHAUS [ IC-HAUS GMBH ]
