TDA5145 Brushless DC motor drive circuit

TDA5145 is a bipolar integrated circuit used to drive3-phase brushless DC motors in full-wave mode. The device is sensorless (saving of 3 hall-sensors) using the back-EMF sensing technique to sense the rotor position.It includes bidirectional control, brake function and has a special circuit built-in to reduce the EMI (soft switching output stages)

TDA5145 offers a sensorless three phase motor drive function. It is unique in its combination of sensorless motor drive and full-wave drive. The TDA5145 offers protected outputs capable of handling high currents and can be used with star or delta connected motors. It can easily be adapted for different motors and applications.

Full-wave driving of a three phase motor requires three push-pull output stages. In each of the six possible states two outputs are active, one sourcing (H) and one sinking(L). The third output presents a high impedance (Z) to the motor, which enables measurement of the motor back-EMF in the corresponding motor coil by the EMF comparator at each output. The commutation logic is responsible for control of the output transistors and selection of the correct EMF comparator. In Table 1 the sequence of the six possible states of the outputs has been depicted.

The zero-crossing in the motor EMF (detected by the comparator selected by the commutation logic) is used to calculate the correct moment for the next commutation,that is, the change to the next output state. The delay is calculated (depending on the motor loading) by the adaptive commutation delay block.