IC-MHM Datasheet, PDF (54/63 Pages) IC-Haus GmbH – 14-BIT ABSOLUTE ANGLE HALL ENCODER

iC-MHM
14-BIT ABSOLUTE ANGLE HALL ENCODER
CALIBRATION
Rev D1, Page 54/63
Complete calibration of the iC-MHM requires setting the
bias current, centering the magnet, and adjusting the
signal conditioning parameters to provide the lowest
distortion sine and cosine signals from the Hall sensors.
Calibration should be performed after configuration and
in the order given following.
Gain Calibration
Calibrate the Hall sensor sine and cosine signal gain by
setting GAINR = 3, GAINF = 0, and ENAC = 1. Reset
the iC-MHM (0x74 = 1) for these values to take effect.
This enables the automatic amplitude control to main-
tain the differential sine and cosine amplitudes at 1V.
Refer to SIGNAL CONDITIONING on page 18 for more
information.
Bias Current Calibration (CIBM)
The internal bias current is calibrated using test mode
and parameter CIBM.
CIBM
Value
0x08
0x09
...
0x0F
0x00 (±0)
0x01
...
0x07
Address 0x06; bits 3:0
Description
50%
56.25%
...
93.75%
100%
106.25%
...
143.75%
With the magnet rotating, move it (or the iC-MHM) along
the PSIN/NSIN diagonal of the iC-MHM (refer to Figure
9 on page 17) until the amplitudes of PSIN (pin 4) and
NSIN (pin 3) are equal. Then, move the magnet or
the iC-MHM along the PCOS/NCOS diagonal until the
amplitudes of PCOS (pin 18) and NCOS (pin 19) are
equal. Iteration may be required for optimum results.
Offset and Gain Correction Cosine Calibration
The sine and cosine offset correction values VOSS
and VOSC, respectively, and the gain correction co-
sine, GCC, can be calibrated automatically or man-
ually. Automatic calibration is performed using the
calibration tab in the free iC-MHM GUI software
(http://www.ichaus.com/MHM). Manual calibration is
performed by configuring the digital I/O port for cali-
bration signal outputs (CFG_IOP = 3) and adjusting the
parameters as explained below.
When configured for calibration signal outputs
(CFG_IOP = 3), the digital I/O port provides the fol-
lowing signals at P1 - P3 (pins 5 - 7, respectively) when
the magnet is rotated continuously.
Table 98: Bias Current Calibration
Figure 42: Calibration Signals
Enable test mode (TEST = 0x19) and measure the bias
current between NSIN (pin 3) and GNDS (pin 16). Ad-
just CIBM until the current is as close to 200 µA as pos-
sible. All internal current sources are then calibrated.
After setting the bias current, disable test mode by set-
ting TEST = 0.
Centering the Magnet
The magnet should be centered on the iC-MHM for low-
est angular error and jitter. If it is possible to adjust the
magnet position relative to the iC-MHM, the centering
can be optimized by equalizing the amplitudes of the
four analog outputs PSIN, NSIN, PCOS, and NCOS.
Adjust VOSS until the duty cycle of the CS_IO1 output
(pin 5) is as close to 50% as possible. Then adjust
VOSC until the duty cycle of the CS_IO2 output (pin
6) is as close to 50% as possible. Finally, adjust GCC
until the duty cycle of the CS_IO3 output (pin 6) is as
close to 50% as possible.
Harmonic Calibration
The harmonic calibration parameter, HARMCAL,
can be set using the free iC-MHM GUI soft-
ware (http://www.ichaus.com/MHM) or by using the
iC-Haus SinCosYzer II Encoder Signal Analyzer
(http://www.ichaus.com/SinCosYzer 2) to measure the
angular error.