Three comparators are provided to process the raw signals from the Hall-effect sensors to commutate the motor. The Hall comparators sense the zero crossings of the differential inputs and pass the information to digital logic. The Hall comparators have hysteresis, and their detect threshold is centered at 0. The hysteresis is defined as shown in Figure 8-39.

In addition to the hysteresis, the Hall inputs are deglitched with a circuit that ignores any extra Hall transitions for a period of t_HDEG after sensing a valid transition. Ignoring these transitions for the t_HDEG time prevents PWM noise from being coupled into the Hall inputs, which can result in erroneous commutation.

If excessive noise is still coupled into the Hall comparator inputs, adding capacitors between the positive and negative inputs of the Hall comparators may be required. The ESD protection circuitry on the Hall inputs implements a diode to the AVDD pin. Because of this diode, the voltage on the Hall inputs should not exceed the AVDD voltage.

Because the AVDD pin is disabled in sleep mode (nSLEEP inactive), the Hall inputs should not be driven by external voltages in sleep mode. If the Hall sensors are powered externally, the supply to the Hall sensors should be disabled if the MCT8316Z device is put into sleep mode. In addition, the Hall sensors' power supply should be powered up after enabling the motor otherwise an invalid Hall state may cause a delay in motor operation.

Figure 8-39 Hall Comparators Operation