IC-MQ_15 Datasheet, PDF (23/43 Pages) IC-Haus GmbH – Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

iC-MQ PROGRAMMABLE 9-BIT
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev F3, Page 23/43
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 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 0x0E, 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 BIASEX = 11 and the sensor’s reference
level connected to input X2 (see Elec. Char. No.
122 for acceptable input voltage).
Table 26: Offset Reference Source CH1, CH2
VDC1
VDC2
Code
0x00
0x01
...
0x20
...
0x3F
Note
Addr 0x07, bit 4:0; Addr 0x06, bit 7
Addr 0x08, bit 6:1
VDCi = (1 − k) · VPi + k · VNi
k = 1/3
k = 0.3386
k = 1/3 + 1/3 · Code/63
k = 0.5026 (center setting)
...
k = 2/3
Adjustment is required only if VOS12 = 0x3
The offset calibration range for CH1 and CH2 is depen-
dent on the selected VOS12 source and 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 0x09, bit 0; Addr 0x08, bit 7
Addr 0x0A, bit 5:4
Range
x1
x2
x6
x12
Table 28: Offset Range CH1, CH2
OF1
OF2
Code
0x00
0x01
...
0x7F
Addr 0xA, bit 3:0; Addr 0x9, bit 7:4
Addr 0xC, bit 0; Addr 0xB, bit 7:1
Factor
Code
Factor
0
0x80
0
+ 0.0079
0x81
− 0.0079
+ OFx /127
...
− (OFx - 128)/127
+1
0xFF
−1
Table 29: 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 adjusted
again (those as amplitude compensation, intermediate
potentials and offset voltages).
PH12
Code
0x00
0x01
...
0x1F
Addr 0xD, bit 2:0; Addr 0xC, bit 7:5
Correction angle Code
Correction angle
0°
0x20
0°
+ 0.65 °
0x21
− 0.65 °
+ 20.2 ° ·
...
PH12 /31
− 20.2 ° ·
(PH12 - 32) /31
+ 20.2 °
0x3F
− 20.2 °
Table 30: Phase Correction CH1 vs. CH2
Table 27: Intermediate Voltages CH1, CH2