IC-MH_17 Datasheet, PDF (14/26 Pages) IC-Haus GmbH – 12-BIT ANGULAR HALL ENCODER

iC-MH
12-BIT ANGULAR HALL ENCODER
reference (1.24 V), with VOSR (0.5 V) used to generate
the range of the offset settings. Bias current IBM deter-
mines 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 individ-
ual iC-MH 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. A CIBM preset value is programmed
to the zapping ROM during chip test by iC-Haus and
therefore no further customer programming is required.
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 C2, Page 14/26
C021107-4
iC-MH
A
B
Z
U
VNA
Test Mode: Analog REF
VREF
IBM
VBG
VOSR
~ 2.5 V
~ 1.24 V
~ 0.5 V
~ 200 µA
Figure 10: 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-MH in relation to one another.
V_sin
+2 V
BIAS Setting
The internal bias setting via register CIBM compensates
for device process tolerances and an optimum setting
value is already pre-programmed into the zapping ROM
by iC-HAUS during automatic chip test. Therefore, no
further customer adjustments are needed for this set-
ting. However, temporary changing the CIBM RAM
content to extreme values can be used to imitate varia-
tions in device characteristic or to simulate changes in
physical parameter like temperature or supply voltage
(see chapter OTP Programming).
α
-2 V
+2 V
V_cos
-2 V
C141107-1
Figure 11: Ideal Lissajous curve
Mechanical Adjustment
iC-MH 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 observed
while the magnet rotates.
In test mode Analog SIN the output signals of the sine
Hall sensors which are diagonally opposite to one an-
other are visible at pins A, B, Z and U. iC-MH 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.
Calibration Using Analog Signals
In test mode Analog OUT as shown in Figure 5 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 in figure 11.
At room temperature and with the amplitude control
switched off (ENAC = 0) 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