MIKROE Brushless 5 Click

Brushless 5 Click is a 3 phase sensorless BLDC motor controller with a soft-switching feature for reduced motor noise and EMI and precise BEMF motor sensing which eliminates the need for Hall-sensors in motor applications. It can drive 5V-16V motors with up to 500 mA current. The motor driver allows speed control via the PWM signal from the host MCU. It also features an output pin for reading the speed of the motor. Delayed phase commutation ensures a reliable motor start while the Lock Detect function prevents damage and overheating. The driver IC requires a low count of external components due to its high degree of integration. Three half-bridge NMOS power outputs are integrated on the IC die and are used to drive the coils of the BLDC motor. Considering all the driving and protection features it has Brushless 5 Click an ideal solution for developing cost-effective and reliable BLDC motor driving applications such as the computer fan coolers power supply fans small BLDC motor applications and similar. Brushless 5 Click uses the A4941 a three-phase sensorless fan driver IC made by Allegro MicroSystems LLC. This IC features a proprietary sensorless BEMF zero-crossing sensing technique which provides a speed reading via the FG output pin routed to the INT pin of the mikroBUS™. The BEMF zero-crossing is the point where the voltage of the undriven motor winding (BEMF is short for Back Electromotive Force) crosses the motor center tap (neutral point) voltage. Neutral point voltage can be approximated using an internally generated reference voltage in the case when the used motor does not provide one. BEMF zero-crossing occurs when a pole of the rotor is in alignment with a pole of the stator and is used as a positional reference for the commutation controller section of the A4941 IC. When the zero-crossing occurs an internal signal is set to a HIGH state while the beginning of the next phase commutation sets this signal to a LOW state. The signal is latched between the states so that commutation transients do not affect it. This provides a robust and accurate position sensing system. The internal sequencer is used to commutate the phases based on the position feedback. During the startup period the phase commutation is provided by the internal oscillator instead until a valid BEMF positional signal sequence is detected. The current through the coils is maximum at this stage since the PWM signal with 100% duty cycle is applied during a start-up sequence. As already mentioned the motor speed can be calculated using the FG output pin. The final calculation will depend on the FG frequency as well as the number of the motor poles and slots. To calculate the actual RPM of the motor the following formula should be applied: ->