Hi everyone,
I’m controlling a DC motor with an STM32 using PWM through a MOSFET driver. The PWM waveform looks clean on the oscilloscope, but the motor produces audible noise and rough movement at lower duty cycles.

The PWM frequency is currently set to 8 kHz.

Questions:

1. Is the noise mainly mechanical, or could switching behavior still be the cause?
2. Would increasing PWM frequency above audible range improve smoothness?
3. On the PCB, should motor current paths be routed separately from logic ground returns?

 

What is the nature of the motor? is it a low pole count maybe?

 

Do you have a suitably rated reverse diode across the motor?