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MCT8316Z: Cannot reach the RPM and efficiency drops in reverse direction

Part Number: MCT8316Z

Hi Team,

Can you please help us with our customer's inquiry below?

I am working on a project that involves the motor driver IC MCT8316ZT. The project is a PCB with onboard BLDC motor and hall sensors. The PCB is a prototype designed by a previous employee, and has issues I am trying to resolve in a new iteration. The main issue is that the motor driver is not working equally in both directions; forward motion is good (CCW), but reverse is bad (CW). I have attached a graph of the performance with 15 degrees of advance (configured by resistor network):

As can be seen from the graph, the reverse power consumption is much higher than forward when going beyond 3500 RPM (I would expect them to be similar in both directions). I have tried multiple ADVANCE values, but 15 degrees seems to be the one that performs the best.

The hall sensors (SS361RT) are placed 120 degrees apart, with the coil and rotor being mounted on top. The motor parts are sourced from the Maxon motor EC45 (200188). Here is a screenshot of the PCB (hall sensors marked with red):

I have tried to desolder the motor coil and hall sensors, and wired an external motor with builtin hall sensors placed 30 degrees apart; https://www.maxongroup.com/maxon/view/product/motor/ecmotor/ecflat/ecflat45/200188. This worked flawless, and thus I suspect the placement of the hall sensors to be the issue. On the external motor the hall sensors are placed differently in multiple ways; they are rotated 90 degrees, placed outside of the stator coils and placed with 30 degrees spacing instead of 120. I have attached an image of the external motor (hall sensors marked with red):

Before I continue with the next iteration of the PCB, I would like to be sure that this issue is addressed, however I am unsure if it is the rotation, angle or placement that is the key difference. Maybe you can guide me in this matter?

Regards,

Danilo