Data Sheet

20

1.10

2018-09-13

TLE4929C Crankshaft Sensor

Fully Programmable Crankshaft Sensor

Figure 18

Signal output in setting “EDGE_POLAR = 0” and “FORWARD_DEF” = 1

The TLE4929C is preprogrammed and has locked EEPROM. In Figure 18 the behavior is pictured when

following conditions are met:

• Backbias magnet is attached with magnetic north pole to the back of TLE4929C. (pictured in left part of

Figure 3.

• Forward-pulses (crank forward pulse-length = 45µsec) are issued when toothed wheel moves from

package-pin 3 (“Q”) to packape-pin 1 (“VDD”).

• Backard-pulses (crank reverse pulse-length = 90µsec) are issued when toothed wheel moves from

package-pin 1(“VDD”) to packape-pin 3 (“Q”).

• The pulse is issued in the middle of the tooth of the toothed wheel.

3.6

System Watchdog

The system watchdog is monitoring following parts in the digital core and at the output:

• Finding valid maxim in the speed signal

• Finding valid minim in the speed signal

• Finding valid zero-crossing of the speed signal

• Monitoring the output switching

As long the speed signal and the corresponding output switching is fine the system watchdog will reset itself

automatically at every output-switching. As soon the system watchdog detects valid maximum, valid

minimum and valid zero-crossing without a switching event at the output, the system watchdog will increase

its counter. Switching of the output sets the counter to zero. When the counter reaches its limit the offset will

be reset.

The advantage of this system watchdog is to avoid “flat line” behavior at the output. Once there happened a

massive event in the sensing system (i.e. hit on the tooth, sudden air gap jump, ...), the TLE4929C is able to

recover itself. The system watchdog can be enabled by EEPROM setting “WATCH_DOG_EN”.

3.7

Stop Start Watchdog

The Stop Start watchdog allows TLE4929C to stay calibrated as much as possible during stand-still of the

target wheel and a possible temperature-drift of 60K. It can be enabled by EEPROM-option.

Basically the Stop Start watchdog is a time-out of 1.4 seconds. After 1.4 seconds time out between two zero

crossing of the speed channel (crankshaft wheel stopped) the Stop Start Watchdog will enter active state. No

output switching is enabled during active watchdog state. After a signal-change in speed channel above DNC

within 1.4 seconds (crankshaft wheel rotates) the TLE4929C will use known signal-amplitude and perform

output-switching with the new switching threshold at the new temperature.

At standstill of the target wheel the stop start watchdog will enable TLE4929C to not issue any wrong pulse at

the output:

• No additional pulses

• No missing pulses

Speed

Direction

Rotation direction CW:

Output „Q“

CW

Rotational

Change

Notch

CW

N

Notch