tle4942 Infineon Technologies Corporation, tle4942 Datasheet - Page 29

• Manufacturer Part Number: tle4942
• Description: Differential Two-wire Hall Effect Sensor-ic For Wheel Speed Applications With Direction Detection
• Manufacturer: Infineon Technologies Corporation

Data Sheet
Fast change of direction signal at small fields:
The described behaviour can happen when rotation direction is changed in
Figure 1
A local extremum (maximum or minimum) of the magnetic input signal can be caused
during a reversal of rotation direction. In this case the local extremum can be detected
by the IC and used for offset calibration. (E.g. the local maximum marked by an arrow in
the above diagram.) Obviously the calculated offset value will be incorrect with respect
to the following signal. As worst case a duty cycle up to max. 15% to 85% could occur
for a few pulses.
After a re-calibration, which typically takes place after 2...3 zero-crossings the offset will
be correct again and hence the duty cycle,
As a result of "bad" duty cycle after fast direction reversal the sampling points for
direction detection are at unusual signal phase angles also. At small magnetic input
signals (∆
max. 7 pulses, in very rare cases (additional PGA transition during calibration similar to
2.) max. 9 pulses.
A local extremum close to the zero-crossing theoretically could lead to distances down
to 45 µs of two consecutive output pulses at the point of direction reversal as well as a
B
warning
pulse also.
B
B
< 1.7 x ∆
-1
-2
-3
3
2
1
0
0
B
warning
100
B
warning
200
and
) this can lead to incorrect direction information. Duration:
300
B
EL
Direction Change of Input Signal at
information can be incorrect during that short period.
400
500
29
B
600
warning
700
and
Time
800
B
EL
also.
900 1000
t
= 690
AED03715
ms
TLE4942-1C
1200
V3.1, 2005-03
TLE4942-1
t
< 0.7 s