IC-MQF_15 Datasheet, PDF (24/38 Pages) IC-Haus GmbH – Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

iC-MQF PROGRAMMABLE 12-BIT ^preliminary
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev C1, Page 24/38
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-MQF 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 automatically
tracks higher DC photocurrents. To this end interme-
diate 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 setting is
altered).
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 or by sup-
ply VDDS.
VOS12
Code
0x0
0x1, 0x2
0x3
Notes
Addr 0x05, bit 5:4
Type of source
Feedback of ACO pin voltage: V(ACO)/20
for supply-dependent differential voltage signals
for Wheatstone sensor bridges
to measure VDDS
Fixed reference: V05 of 500 mV, V025 of 250 mV
for single-ended current or voltage signals
for single-ended or differential stabilized signals
(regulated sensor or waveform generator)
Self-tracking sources VDC1, VDC2 (125...250 mV)
for differential current signals
for differential voltage signals*
*) Requires MUX(5:4) = 3 and the sensor’s reference
connected to input X2; refer to Elec. Char. No. 105
for acceptable input voltage).
Table 22: Offset Reference Source CH1, CH2
VDC1
VDC2
Code
0x000
0x001
...
0x200
...
0x3FF
Notes
Addr 0x0E, bit 1:0; Addr 0x0D, bit 7:0
Addr 0x0F, bit 5:0; Addr 0x0E, bit 7:4
VDCi = (1 − k) · VPi + k · VNi
k = 1/3
k = 0.3386
k = 1/3 + 1/3 · Code/1023
k = 0.5000 (center setting)
...
k = 2/3
Adjustment is required only if VOS12 = 0x3
The offset calibration range for CH1 and CH2 is set
using OR1 and OR2. Both sine and cosine signals
are then calibrated using factors OF1 and OF2. The
calibration target is reached when the DC fraction of
the differential signals PCHi versus NCHi is zero.
OR1
OR2
Code
0x0
0x1
0x2
0x3
Addr 0x10, bit 1:0
Addr 0x10, bit 3:2
Range
x1
x2
x6
x12
Table 24: Offset Range CH1, CH2
OF1
OF2
Code
0x000
0x001
...
0x3FF
Addr 0x11, bit 6:0; Addr 0x10, bit 7:4
Addr 0x13, bit 2:0; Addr 0x12, bit 7:0
Factor
Code
Factor
0
0x400
0
0.00098
0x401
− 0.00098
+ Code / 1023
...
− (Code - 1024)
/ 1023
1
0x7FF
−1
Table 25: Offset Factors CH1, CH2
Phase Correction CH1 vs. CH2
The phase shift between CH1 and CH2 can be adjusted
using parameter PH12. Following phase calibration
other calibration parameters may have to be readjusted
(those as amplitude compensation, intermediate poten-
tials and offset voltages).
PH12
Code
0x000
0x001
...
0x1FF
Addr 0x14, bit 5:0; Addr 0x13, bit 7:4
Correction angle Code
Correction angle
0°
0x200
0°
+ 0.0204 °
0x201
− 0.0204 °
+ 10.42 ° ·
...
PH12 /511
− 10.42 ° ·
(PH12 - 512) /511
+ 10.42 °
0x3FF
− 10.42 °
Table 26: Phase Correction CH1 vs. CH2
Table 23: Intermediate Voltages CH1, CH2