TLE4955C Datasheet, PDF (6/21 Pages) Infineon Technologies AG – Differential Hall Effect Transmission Speed Sensors

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TLE4955C
Operating Modes and States
2
Operating Modes and States
2.1
Uncalibrated and Calibrated Mode
After power on the differential magnetic speed signal is tracked by an analog to digital converter (Tracking
ADC) and monitored within the digital core. If the signal slope is identified as a rising edge, the first output
pulse is triggered. A second trigger pulse is issued as soon as the next rising edge is detected (see Figure 4 ). In
uncalibrated mode, the output protocols are triggered by the DNC (detection noise constant) in the speed
path. After start up the first DNC value is set to 2xΔB_{speed- limit} and after that the DNC is adapted to the magnetic
input signal amplitude (ΔB_speed) with a minimum of 2xΔB_speed-limit.
The offset update starts if two valid extrema values are found and the direction of the update has the same
orientation as the magnetic signal. For example, a positive offset update is being issued on a rising magnetic
edge only. The offset update is done independent from the output switching. After a successful offset
correction, the sensor is in calibrated mode. Switching occurs at the adaptive hysteresis threshold level.
In calibrated mode, the DNC is adapted to magnetic input signal amplitude (as ΔB_speed /2) with a minimum of
2xΔB_speed-limit. The output pulses are then triggered with adaptative hysteresis.
In uncalibrated mode (after start-up or reset) for signals with amplitude smaller than 2*ΔB_limit (either for
direction or speed signal), the sensor always provides the first two pulses and could suppress the third one.
The pulse corresponding to the fourth magnetic period is calibrated, thus including the direction information.
Data Sheet
6
Version 1.0
2016-06-15