tle4942 Infineon Technologies Corporation, tle4942 Datasheet - Page 9

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

TLE4942-1
TLE4942-1C
is switched into a low-jitter mode, thereby avoiding oscillation of the offset DAC LSB.
Switching occurs at zero-crossover of the differential magnetic signal. It is only affected
by the small residual offset of the comparator and by the propagation delay time of the
signal path, which is mainly determined by the noise limiting filter. Signals which are
below a predefined threshold ∆
B
are not detected. This prevents unwanted switching.
Limit
The comparator also detects whether the signal amplitude exceeds ∆
B
or ∆
B
.
Warning
EL
This information is fed into the DSP and the output encoder. The pulse length of the High
output current is generated according to the rotational speed, the direction of rotation
and the magnetic field strength.
Direction Signal Circuitry
The differential signal between a third Hall probe and the mean of the differential Hall
probe pair is obtained from the direction input amplifier. This signal is digitized by the
direction ADC and fed into the DSP circuitry. There, the phase of the signal referring to
the speed signal is analyzed and the direction information is forwarded to the output
encoder.
Additional Notes
Typically the phase error due to PGA-transition reduces the error caused by switching
the mode from uncalibrated to calibrated.
In very rare cases a further PGA switching can occur during the calibration process. It
can take place when the signal is extremely close to a PGA switching threshold. This
additional switching might delay the transition to calibrated mode by two more pulses.
The probability of this case is mainly depending on variations of magnetic amplitude
under real automotive conditions (see Appendix B)
The direction detection feature is also active in the uncalibrated mode but only at
substantial magnetic signal. The correct direction information is worst case available
after the first two output pulses in calibrated mode. Regarding the rare case mentioned
before combined with other initial conditions this may lead to a worst case of 9 pulses
before correct direction information is guaranteed.
Package Information
Pure tin covering (green lead plating) is used. Leadframe material is Wieland K62 (UNS:
C18090) and contains CuSn1CrNiTi. Product is ROHS compliant and may contain a
data matrix code on the rear side of the package.
Data Sheet
9
V 3. 1, 2005-02