CCS/DRV8305: High frequency motor noise

Part Number:DRV8305

Tool/software: Code Composer Studio

Hi,

I'm using a custom designed board to run a sensorless BLDC motor using a DRV8305 driver and TMS320F28027 microcontroller.

Under loaded condition, the motor makes a high frequency (1kHz - 2kHz) audible noise (almost like a whistle). I've made the following observations so far:

• I've noticed that this noise is related to the PWM frequency. So far the best result I've seen is on 23kHz.
• The same noise can be heard while performing motor parameters identification using lab2b.
• The noise varies between motors belonging to the same build batch.
• The noise tends to be noticeable and louder during lower ambient temperatures.

Does anyone know the cause of this noise and how to eliminate/minimize it?

Thanks.