IC-MH16_15 Datasheet, PDF (15/25 Pages) IC-Haus GmbH – 12-BIT ANGULAR HALL ENCODER

iC-MH16
12-BIT ANGULAR HALL ENCODER
preliminary
ate the range of the offset settings. Bias current IBM
determines the internal current setting of the analog
circuitry. In order to compensate for variations in this
current and thus discrepancies in the characteristics of
the individual iC-MH16 devices (due to fluctuations in
production, for example), this can be set within a range
of -40 % to +35 % using register parameter CIBM. The
nominal value of 200 µA is measured as a short-circuit
current at pin B to ground.
Test mode Digital CLK
If, due to external circuitry, it is not possible to measure
IBM directly, by way of an alternative clock signal CLKD
at pin A can be calibrated to a nominal 1 MHz in this
test mode via register value CIBM.
Rev A1, Page 15/25
iC-MH16 ^{Test Mode: Analog REF}
A
VREF
~ 2.5 V
B
IBM
Z
VBG
~ 1.24 V
NA
VOSR
~ 0.5 V
D250814-4
VNA
~ 200 µA
Figure 12: Setting bias current IBM in test mode Ana-
log REF
CALIBRATION PROCEDURE
The calibration procedure described in the following ap-
plies to the optional setting of the internal analog sine
and cosine signals and the mechanical adjustment of
the magnet and iC-MH16 in relation to one another.
V_sin
+2 V
BIAS setting
The BIAS setting compensates for possible manufac-
turing tolerances in the iC-MH16 devices. A magnetic
-2 V
field does not need to be present for this setting which
can thus be made either prior to or during the assembly
of magnet and iC-MH16.
α
+2 V
V_cos
If the optional setup process is not used, register CIBM
should be set to an average value of 0x8 (which is
equivalent to a change of 0 %). As described in the
previous section, by altering the value in register CIBM
in test mode Analog REF current IBM is set to 200 µA
or, alternatively, in test mode Digital CLK signal CLKD
is set to 1 MHz.
Mechanical adjustment
iC-MH16 can be adjusted in relation to the magnet in
test modes Analog SIN and Analog COS, in which the
Hall signals of the individual Hall sensors can be ob-
served while the magnet rotates.
In test mode Analog SIN the output signals of the sine
Hall sensors which are diagonally opposite one another
are visible at pins A, B, Z and NA. iC-MH16 and the
magnet are then adjusted in such a way that differen-
tial signals V_PSIN and V_NSIN have the same amplitude
and a phase shift of 180 °. The same applies to test
mode Analog COS, where differential signals V_PCOS
and V_NCOS are calibrated in the same manner.
-2 V
C141107-1
Figure 13: Ideal Lissajous curve
Calibration using analog signals
In test mode Analog OUT as shown in Figure 6 the
internal signals which are transmitted to the sine/digital
converter can be tapped with high impedance. With a
rotating magnet it is then possible to portray the differ-
ential signals V_SIN and V_COS as an x-y graph (Lissajous
curve) with the help of an oscilloscope. In an ideal setup
the sine and cosine analog values describe a perfect
circle as a Lissajous curve, as illustrated by Figure 13.
At room temperature and with the amplitude control
switched off (ENAC = 0x0) a rough GAING setting is se-
lected so that at an average fine gain of GAINF = 0x20
(a gain factor of ca. 4.5) the Hall signal amplitudes are
as close to 1 V as possible. The amplitude can then be
set more accurately by varying GAINF. Variations in the
gain factor, as shown in Figure 14, have no effect on