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Hysteresis concept:

There are two different hysteresis concepts implemented in the IC.

The first one is called visible hysteresis, meaning that the output switching levels are

changed between two distinct values (depending on the direction of the magnetic field

during a switching event), whenever a certain amount of the magnetic field has been

passing through after the last switching event. The visible hysteresis is used in the

precalibrated mode of unprogrammed sensors. See fig.1 for more details.

The second form of hysteresis is called hidden hysteresis. This means, that one cannot

observe a hysteresis from outside. If the value of the switching level does not change,

the output always switches at the same level. But inside the IC there are two distinct

levels close above and below the switching level, which are used to arm the output. In

other words if the value of the magnetic field crosses the lower of this hysteresis levels,

then the output will be able to switch if the field crosses the switching level. After this

switching event the output will be disabled until the value of the magnetic field crosses

one of the two hysteresis levels. If it crosses the upper hysteresis level, then the output

will be armed again and can switch if the magnetic field crosses the switching level. On

the other hand, if the magnetic field does not reach the upper hysteresis level, but the

lower hysteresis level will be crossed again after a switching event, then the output is

allowed to switch, so that no tooth will be lost. But please notice that this causes an

additional phase error. The hidden hysteresis is used for programmed sensors in

precalibrated and calibrated mode. For more details see fig.2