MCF8315A: BLDC QUESTIONS

Ruixin Feng

Part Number: MCF8315A
Other Parts Discussed in Thread: MCT8316Z

Hi team,

I got several questions from customer. could you pls help to comment on it? Thanks!

1. How does the algorithm estimate the angle? What is the accuracy of the estimated angle? Does it affect the actual speed of the motor rotor? How much error is there?
2. Is angle estimation only supported by MCF8315? According to the MCF8315X device selection manual, if the peak winding current of the application does not exceed 5A, 
    can it be understood that the performance of 8315 is better than that of 8316?
3. Is it possible to achieve extremely low speed control using sensorless FOC?

Rayna

over 1 year ago

0 Joshua Horlander Cruz over 1 year ago

TI__Mastermind 23750 points

Hi Ruixin,

Can you tell me the application that the customer is looking to use our device for? From the questions asked I get the feeling that they are looking to use our device for precision control is this correct?

Regards,

Joshua

0 Ruixin Feng over 1 year ago

TI__Intellectual 2375 points

Hi Joshua,

they plan to use it to do Blood pump control on dialysis machine.

Could you pls give some comments on the questions?

Rayna

0 Ruixin Feng over 1 year ago in reply to Joshua Horlander Cruz

TI__Intellectual 2375 points

Yes, they want to use for precision control. Is it recommended? Customer want to run BLDC at very low speed cause if customer use square waveform, the startup speed will be too fast.

0 Joshua Horlander Cruz over 1 year ago in reply to Ruixin Feng

TI__Mastermind 23750 points

Hi Ruixin,

If the customer needs high accuracy of the motor position and cannot let the motor spin quickly at startup then a non-sensored solution may not be the best device. For low speed solutions that cannot have the startup have higher speeds we recommend using a sensored solution, such as the MCT8316Z, as this algorithm does not need to determine the BEMF which can lead to fast start up speeds depending on the motor.

Ruixin Feng said:
Is it possible to achieve extremely low speed control using sensorless FOC?

Typically we can achieve 5% of max speed with out MCF83xx devices, however lower speeds have been able to be achieved depending on the motors parameters. Please see the following E2E post for more information: https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1231223/mcf8315a-rotation-speed-of-the-motor

Ruixin Feng said:
Is angle estimation only supported by MCF8315?

Angle estimation output though the DCAOUT pin is also supported on the MCF8316C-Q1 and the MCF8329 which is planned to be released in Q1-2024.

Ruixin Feng said:
How does the algorithm estimate the angle? What is the accuracy of the estimated angle? Does it affect the actual speed of the motor rotor? How much error is there?

To determine the angle of the motor the DACOUT pin can be set to output a waveform which will rise from 0V to 3.3V as the rotor moves from 0 to 360 degrees when in estimated rotor angle mode. The intention is that this signal be fed to an external microcontroller which will interpret the angle of the motor from the voltage level of the DACOUT signal. Please see this E2E post for more information: https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1273224/mcf8315a-simple-position-control-with-bldc

Regards,

Joshua

Motor drivers

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MCF8315A: BLDC QUESTIONS