MCF8329A: Query on Disabling Internal Speed Loop and Using External PID with Encoder Feedback in MCF8329A

Part Number: MCF8329A
Other Parts Discussed in Thread: MCF8329HS

Hi TI team,

I am currently working with the MCF8329A BLDC motor driver interfaced with an STM32 microcontroller for a speed-controlled application.
System details:

• Motor equipped with an incremental encoder (accuracy ~1%)
• External controller: STM32 (implementing control logic)
• Current driver mode: Closed-loop FOC with internal speed loop

Observation:
The internal speed loop of the MCF8329A, which relies on FOC-based estimation, provides speed regulation accuracy of <3%. This is not sufficient for our application, especially since we have access to a higher-accuracy encoder feedback (~1%).

Requirement:
We intend to:

1. Use encoder feedback directly in the STM32.
2. Implement an external PID controller for speed regulation.
3. Adjust motor drive (PWM duty cycle / command input) based on this external PID output.

Queries:

1. Is it possible to disable or bypass the internal speed loop of the MCF8329A while still using its FOC commutation?
2. Can the device be operated in a mode where torque or current control is internal, but speed control is fully external?
3. What is the recommended method to interface an external speed loop (via MCU) with the MCF8329A?
4. Are there any constraints or stability considerations when cascading an external speed loop over the internal current/FOC loop?

Goal:
To achieve speed regulation accuracy close to encoder limits (~1%) while still leveraging the MCF8329A’s FOC capabilities for efficient motor control.

Any application notes, configuration guidelines, or reference designs for this architecture would be highly appreciated.

Thanks and regards,
Anirudh