The TMAG511x samples the Hall element at a nominal sampling interval of tPD to detect the presence of a magnetic south pole. Between each sampling interval, the device calculates the average magnetic field applied to the device. If this average value crosses the BOP or BRP threshold, the device changes the corresponding level as defined in Figure 8-21. Because the system, Hall sensor + magnet is by nature asynchronous, the propagation delay td will vary depending on when the magnetic field goes above the BOP value. As shown in Figure 8-20 the output delay will then depend on when the magnetic field will get higher than the BOP value. The first graph shows the typical case. The magnetic field goes above the BOP value at the moment where the output is updated. The part will then only need one cycle of tPD to update the output. The second graph shows a magnetic field going above the BOP value just right before half of the sampling period. This is the best case possible where the output will be updated in just half of the sampling period. Finally, the third graph shows the worst possible case where the magnetic field goes above the BOP value just after half of the sampling period. At the next output update, the value will still see a value under the threshold and will need a whole new period to update the output.
Figure 8-21 shows TMAG511x propagation delay analysis when a magnetic south pole is applied. The Hall element of the TMAG511x experiences an increasing magnetic field as a magnetic south pole approaches near the device as well as a decreasing magnetic field as a magnetic south pole leaves away. At time t1 the magnetic field goes above the BOP threshold. The output will then start to move after the time tPD. This time will vary depending on when the sampling period is, as shown in Figure 8-21. At t2 the output start pulling to the low voltage value. At t3 the output is completely pulled down to the lower voltage value. The same process happen on the other way when the magnetic value is going under the BOP threshold.