|
IC-MQF Datasheet, PDF (24/37 Pages) IC-Haus GmbH – PROGRAMMABLE 12-BIT Sin/Cos INTERPOLATION IC WITH RS422 DRIVER | |||
|
◁ |
iC-MQF PROGRAMMABLE 12-BIT preliminary
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev A1, Page 24/37
Offset Calibration CH1, CH2
In order to calibrate the offset the reference source
must ï¬rst be selected using VOS12. Two ï¬xed voltages
and two dependent sources are available for this pur-
pose. The ï¬xed 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 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 setting is
altered).
The feedback of pin voltage V(ACO) fulï¬lls 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 sensorâs
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 â 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 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
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
â 0.00098
+ Code / 1023
...
â (Code - 1024)
/ 1023
1
0x7FF
â1
Table 25: 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
readjusted (those as amplitude compensation, inter-
mediate potentials 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
â 0.0204 °
+ 10.42 ° ·
...
PH12 /511
â 10.42 ° ·
(PH12 - 512) /511
+ 10.42 °
0x3FF
â 10.42 °
Table 26: Phase Correction CH1 vs. CH2
Table 23: Intermediate Voltages CH1, CH2
|
▷ |