Data Sheet

4

Ver. 1.0

2019-07

TLE4959-5U-R Transmission Speed Sensor

Functional Description

1.3

Basic Operation

The speed signal calculated out of the differential hall elements, is amplified, filtered and digitized. An

algorithm in the digital core for peak detection and offset calculation will be executed. The offset is fed back

into the speed signal path with a digital to analog converter for offset correction. During uncalibrated mode,

the output of the speed pulse is triggered in the digital core by exceeding a certain threshold of the tracking

ADC. In calibrated mode the output is triggered by the visible hysteresis.

The direction signal is calculated out of center Hall signals. The direction signal is amplified, filtered, and

digitized. In the digital core the direction and the vibration detection information is determined and the

output protocol is issued.

1.4

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 or falling edge, the

first output pulse is triggered. A second trigger pulse is issued with direction information.

In uncalibrated mode, the output protocols are triggered by the DNC (detection noise constant) in the speed

path. After start up the sensor switches with the DNC min value and after that the DNC is adapted to the

magnetic input signal amplitude.

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. 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 with a minimum of

1.5

Hysteresis Concept

The adaptive hysteresis is linked to the input signal. Therefore, the system is able to suppress switching if

vibration or noise signals are smaller than the adaptive hysteresis levels. The typical value for the hysteresis

The visible hysteresis keeps the excellent performance in large pitch transmission application wheels.

Figure 4

Adaptive Hysteresis

-10

-8

-6

-4

-2

0

2

4

6

8

10

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

time [s]

Hysteresis = 0.25 *

magnetic input signal

hysteresis HI

hysteresis LO