iC-TW4 PROGRAMMABLE INTERPOLATOR
WITH AUTOMATIC OFFSET CORRECTION
Rev D1, Page 10/14
Test
[V] at CFG1 Z at CFG1 [V] at CFG2
Z at CFG2
mode
PGA A 0.8 * VDD
PGA B 0.8 * VDD
Calib 1 0.87 * VDD > 75 kΩ
< 3 kΩ
> 75 kΩ
Refer to table 8 > 75 kΩ
Refer to table 8 > 75 kΩ
Refer to table 8 < 3 kΩ
Refer to table 8 < 3 kΩ
Index
cali-
0.87 * VDD < 3 kΩ
bration
Offset
Vc
0.87 * VDD < 3 kΩ
0.87 * VDD > 75 kΩ
Refer to table 8 > 75 kΩ
Refer to table 8 > 75 kΩ
Table 9: Test modes
INDEX GATING
The iC-TW4 can interface to a wide range of index gat- open drain stage pulling the output low in the presence
ing sources. Most commonly used are the digital Hall of a magnetic field. The unused terminal NINZ or PINZ
sensor and the MR sensor bridge. The digital Hall sen- should be biased to an adequate mid voltage level to
sor provides a large swing input signal to the iC-TW4. guarantee good noise margin. Refer to Figure 5 for
Depending on the polarity of the Hall it is either con- sample configurations.
nected to pin NINZ or PINZ. Most Hall sensors use an
VDD
VDD
VDD
PINZ
PINZ
PINZ
VDD
NINZ
MR index
sensor
iC-TW4
NINZ
iC-TW4
iC-TW4
NINZ
Digital Hall
active low
Index gating using
Hall sensor
Index gating
using MR bridge
no Index
Figure 5: Index configuration
A MR sensor differential bridge can also be used to gating window to be observed. This simplifies prod-
gate the index. Typically, the MR sensor provides a uct calibration as variation in sensor offset can be eas-
small signal amplitude. In addition, residual side lobes ily compensated for. Figure 6 shows a correctly set
are present that can trigger double indexing. It might threshold when using an MR gating sensor. The side
be necessary to externally adjust the sensor offset in lobes are below the threshold line and no parasitic trig-
order to fine-tune the desired threshold. The iC-TW4 gering occurs.
provides a calibration mode, which allows the internal
ICHAUS [ IC-HAUS GMBH ]
