IC-MU_17 Datasheet, PDF (22/66 Pages) IC-Haus GmbH – MAGNETIC OFF-AXIS POSITION ENCODER - POLE WIDTH 1.28MM

iC-MU MAGNETIC OFF-AXIS
POSITION ENCODER - POLE WIDTH 1.28MM
ANALOG SIGNAL CONDITIONING FLOW: x = M,N
Rev D1, Page 22/66
For the purpose of signal conditioning iC-MU has sev-
eral settings that make internal reference values and
the amplified Hall voltages of the individual sensors ac-
cessible at the outer pins of PORT B for measurement.
This allows the settings of the amplifier (GC_x, GF_x),
the amplitude ratio of cosine to sine signal (GX_x), and
the offset (VOSS_x , VOSC_x) and phase (PH_x) of the
master (x = M) and nonius tracks (x = N) to be directly
observed on the oscilloscope.
Note:
For an easy instaltion and setup, the analog and
the track offset SPON correction should be done by
using the automatic calibration functions of the GUI
software (or DLL) available for iC-MU. All necessary
steps are described in the iC-MU application note
AN3: http://www.ichaus.de/MU_AN3_appnote_en
Test mode can be programmed using register TEST
(address 0x18). The individual test modes are listed in
Table 24 and 25.
Test mode output signals
Mode
TEST Pin PB0
Normal
0x00
Analog Master 0x01 PSM
Analog CNV_M 0x03 PSIN_M
Analog Nonius 0x11 PSN
Analog CNV_N 0x13 PSIN_N
Pin PB1
NSM
NSIN_M
NSN
NSIN_N
Pin PB2 Pin PB3
PCM
PCOS_M
PCN
PCOS_N
NCM
NCOS_M
NCN
NCOS_N
Table 25: Testmodes and available output signals
The output signals of the signal path are available as
differential signals with a mean voltage of half the sup-
ply voltage and can be selected for output according to
Table 25.
2. Positioning of the sensor
Next, the sensor should be adjusted in relation to the
magnetic code carrier. The value of MPC (Table 52)
has to be selected according to the magnetic code car-
rier. The register values for VOSS_x, VOSC_x, GX_x
and PH_x are set to 0. The chip position will now be
displaced radially to the magnetic code carrier until the
phase shift between the sine and cosine is 90°.
Note:
MODEB must be set to 0x0 before selecting a test
mode.
Test Mode output signals
Mode
TEST Pin PB0
Normal
0x00
Analog REF 0x1F VREF
Digital CLK 0x26 -
Pin PB1
VBG
-
Pin PB2
IBM
-
Pin MTC
-
CLK
Table 24: Test modes for signal conditioning
Depending on the mounting of the system it may be
necessary to displace iC-MU tangentially to the mag-
netic code carrier to adjust the amplitude between the
sine and cosine signals.
A fine adjustment of the analog signals is made with
the registers described in the chapter SIGNAL CONDI-
TIONING FOR MASTER AND NONIUS CHANNELS
page 20.
The adjustment should be made in the order:
1. Conditioning the BIAS current
First of all, the internal bias is set. The BIAS current is
adjustable in the range of -40 % to +35% to compen-
sate variations of this current and thus differences in
characteristics between different iC-MU (e.g. due to
manufacturing variations). The nominal value of 200 µA
is measured as a short-circuit current at pin PB2 refer-
enced to VNA in test mode 0x1F.
Additionally various internal reference voltages are
available for measuring in this test mode. VREF corre-
sponds to half the supply voltage (typically 2.5 V) and is
used as a reference voltage for the hall sensor signals.
VBG is the internal bandgap reference (1.25 V)
Alternatively the frequency at Pin MTC can be adjusted
to
405
kHz
(
fosc
64
,
see
elec.
char.
no.:
407)
using
register
value CIBM in test mode 0x26, if an analog measuring
of the current is not possible.
1. phase
2. amplitude
3. offset
3.a Test modes analog master and analog nonius
In these test modes the amplified, conditioned signals
are presented to port B. These signals can be charged
with a maximum of 1 mA and should not exceed a dif-
ferential voltage of 0.5 Vpp.
3.b Test mode CNV_x
In this test mode the sensor signals are present at port
B as they are internally for further processing on the
interpolator. The achievable interpolation accuracy is
determined by the quality of signals PSIN_x/NSIN_x
and PCOS_x/NCOS_x and can be influenced in this
test mode by adjustment of the gain, amplitude ratio,