TLE4955C Datasheet, PDF (8/21 Pages) Infineon Technologies AG – Differential Hall Effect Transmission Speed Sensors

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TLE4955C
Operating Modes and States
2.3
Direction Detection
The difference between the Hall element signal B₃ and the mean value of the outer Hall elements B₂ and B₁ will
be calculated in the direction input amplifier. This signal is digitized by an analog to digital converter
(direction ADC) and fed into the digital core.
Depending upon the rotation direction of the target wheel, the signal of the center probe anticipates or lags
behind for 90°. This phase relationship is evaluated and converted into rotation direction information by
sampling the signal of the center probe in the proximity of the zero crossing of the “speed” bridge signal.
The first pulse after power on is a speed pulse, as there is no valid direction information available.
2.4
Vibration Suppression
The magnetic signal amplitude and the direction information are used for detection of parasitic magnetic
signals. Unwanted magnetic signal can be caused by angular or air gap vibrations. If an input signal is
identified as a vibration the output pulse will be suppressed.
TLE4955C offers two different kinds of vibration suppression:
• Vibration suppression via hysteresis. This is available after power on
• Vibration suppression via direction detection. This is available after start up calibration is performed.
2.5
Undervoltage Behavior
At the first switching events after power on the undervoltage detection is activated.
If the supply voltage drops below the values specified in operating range, an active output (defined state) will
be generated. The output level is switched to high current (I_High) and it remains at this level until the supply
voltage reaches again the functional level.
V_{D D}
on IC leads
VDD
on IC
leads
V_Reset
VDD voltage drops due to
increased current throught R M
I_{D D}
curr^Ie^Hnⁱt^gh
1st switching enables
VDD reset
switches to I_high
due to undervoltage
The sensor starts with
power on process
Release
I_Low
Startup
Mode
Operating Mode
Figure 6 Undervoltage Behavior
Undervoltage
pre -low bit
Operating Mode
If the supply voltage is below 2.3 V typical the sensor will reset and initiate a new calibration.
Data Sheet
8
Version 1.0
2016-06-15