IC-MHM Datasheet, PDF (18/63 Pages) IC-Haus GmbH – 14-BIT ABSOLUTE ANGLE HALL ENCODER

iC-MHM
14-BIT ABSOLUTE ANGLE HALL ENCODER
SIGNAL CONDITIONING
Rev D1, Page 18/63
The iC-MHM provides conditioning of the Hall signals
to equalize amplitudes, remove offsets, and correct
harmonic distortion. An automatic amplitude control is
provided which maintains optimum signal amplitudes
despite changes in air gap between the magnet and the
iC-MHM, temperature, or supply voltage. All correction
values must be determined individually for every device
and set manually.
Coarse Gain Range (GAINR)
The Hall signals are amplified in two stages. The first
stage amplifier gain is set using parameter GAINR.
Automatic Amplitude Control Enable (ENAC)
The integrated automatic amplitude control is enabled
using bit ENAC. It is recommended to always use the
automatic amplitude control to ensure that the interpo-
lator is operating with optimum signal levels.
ENAC
Value
0
1
Address 0x09; bit 7
Description
Automatic Amplitude Control Disabled
Automatic Amplitude Control Enabled
Table 10: Automatic Amplitude Control Enable
GAINR
Value
0
1
2
3
Address 0x08; bits 7:6
Coarse Gain Range
5
10
14.5
17.5
When enabled, the automatic amplitude control main-
tains the amplitude of the differential sine and cosine
signals at 1 Vpp by varying GAINR and GAINF from
their initial values as required. The sine and cosine
signals can be monitored at the PSIN, NSIN, PCOS,
and NCOS outputs as shown in Figure 13.
Table 8: Coarse Gain Range
Note: A coarse gain range of 17.5 (GAINR = 3) should
be used initially as part of the default configuration.
After setting the gain, a Reset instruction must be ex-
ecuted via BiSS or SPI for the changed parameter to
take effect. Refer to INSTRUCTION REGISTERS on
page 32 for more information.
PSIN
NSIN
250mv
PSIN-NSIN
1Vpp
PCOS-NCOS
Fine Gain (GAINF)
The second amplifier stage provides a fine gain adjust-
ment using parameter GAINF.
Figure 13: Hall Signal Amplitudes with Automatic
Amplitude Control Enabled
GAINF
Value
0x00
0x01
...
0x3F
Address 0x08; bits 5:0
Fine Gain
1.000
1.048
exp(
ln(20)
64
·
GAINF)
19.08
Table 9: Fine Gain
Note: A fine gain of 1.000 (GAINF = 0x00) should be
used initially as part of the default configuration. After
setting the gain, a Reset instruction must be executed
via BiSS or SPI for the changed parameter to take
effect. Refer to INSTRUCTION REGISTERS on page
32 for more information.
When automatic gain control is enabled, the gain con-
trol value use at any time is available in the gain status
register. Refer to STATUS REGISTERS on page 30 for
more information.
If the Hall signal amplitudes are too low even with max-
imum gain, bit ERR_AMIN in the error status register
is set, the error output is activated (pin NERR low),
and the error bit in the BiSS SCD, SPI position read
command response, and extended SSI frame are also
activated (nERR = nE = 0). Likewise, if the Hall signal
amplitudes are too large even with minimum gain, bit
ERR_AMAX is set, the error output is activated (pin
NERR low), and the error bit in the BiSS SCD, SPI posi-
tion read command response, and extended SSI frame
are also activated (nERR = nE = 0). Refer to STATUS
REGISTERS on page 30 for more information.