Data Sheet

14

1.10

2018-09-13

TLE4929C Crankshaft Sensor

Fully Programmable Crankshaft Sensor

3.3.1

Power-on Phase

The operation in Power-on Phase is to refresh the trimming coefficients and algorithm settings from the

EEPROM and to allow the signal path to stabilize.

If an unrecoverable error is found at EEPROM refresh, the output will remain locked HIGH during the entire

operation.

3.3.2

Initial Phase

The magnetic field is measured by three chopped Hall probes. From the outer Hall probes located at a

distance of 2.5mm a differential magnetic field is measured which is named “speed” in this datasheet. From

the center Hall probe the “direction” signal is derived. Both signals are converted to a digital value via an ADC.

3.3.3

Calibration Phase

The adaptation of the threshold to the magnetic field is performed in Calibration Phase. This adaptation is

done based on the field values set by teeth and notches (or based on poles on the pole wheel). These

variations in the magnetic field are followed by a local extrema detection state machine in the IC. During

Calibration Phase the IC permanently monitors the magnetic signal. First and second switching is performed

when the speed-path recognized a certain change of magnetic field and the polarity meets the switching

criterion derived from the EEPROM. The third and further pulse of the output is performed at “zero-crossing”

of the speed path. “Zero crossing” is the 50%-value between detected minimum and detected maximum - also

known as “offset”.

3.3.4

Running Phase

According to the choosen algorithm in EEPROM an avaerage of 5 to 58 pulses is used to do an offset-calculation

and an offset-update.

The following rules have to be verified before applying a computed update to the threshold register:

• Compatibility between threshold update sign and magnetic edge

• Threshold update has to be large enough not to be discarded (minimum_update)

• Threshold update is limited to a maximum value based on field amplitude and on comparison with

absolute field value (maximum_update)

• Computed threshold update is always halved before being applied

• Threshold update is filtered to discourage consecutive updates in opposite direction

(consecutive_upd_req)

Typically the offset is updated after one complete revolution of the target wheel, which is effectively 58 teeth.

Table 5

Available offset update algorithm to be choosen in EEPROM

Parameter

Symbol

Values

Unit Note or Test Condition

Min. Typ. Max.

Offset update

algorithm

58 teeth

-

58

-

-

one revolution of a 60-2 target

32 teeth

-

32

-

-

one revolution of a 32-teeth /pole-pair

target

5 times the same sign

for offset-update

5-

-

-

suggested for wheels with different

number of teeth or for large run-out.