MCF8316A: Very low speed control

Stephen Hughes1

Part Number: MCF8316A
Other Parts Discussed in Thread: MCT8316Z

I see from another thread that the MCF8316A struggles with speeds <10%. Is there any way to overcome this, or do TI offer another driver which can work at lower speeds?

We have an application where we need to control a 4000 RPM motor down to under 1 RPM. I have seen some manufacturers offer complete driver solutions which can handle this, but we are intending to produce this product in volume so these options are not cost effective.

We are currently trialing a stepper, but heat is an issue thus looking to BLDC as an alternative.

over 3 years ago

0 Vishnu Balaraj over 3 years ago

TI__Mastermind 24415 points

Stephen,

Is your motor coupled to a gear that should spin under1 RPM? Does your motor have sensors such as Hall, encoder? Without sensors, it will not be possible to spin a motor under 1 rpm for a sensorless BLDC motor driver.

Regards,

Vishnu

0 Aaron Barrera over 3 years ago in reply to Vishnu Balaraj

TI__Mastermind 26046 points

Hi Stephen,

Do you still need assistance on this thread? If not, please mark as Resolved.

Thanks,
Aaron

0 Stephen Hughes1 over 3 years ago in reply to Vishnu Balaraj

Prodigy 160 points

We will be using a gearbox, yes, but we need 1 RPM shaft speed on the motor as the final drive speed we need is around 0.01 RPM.

We have the flexibility to choose the necessary motor, however cost is an issue, as always, so avoiding expensive sensors would be ideal.

0 Vishnu Balaraj over 3 years ago in reply to Stephen Hughes1

TI__Mastermind 24415 points

Stephen,

Trying to spin a 4000 rpm rated motor at 1 RPM will be quite challenging for any Sensorless FOC driver. I think you should start looking for sensored solutions.

Regards,

Vishnu

0 Stephen Hughes1 over 3 years ago in reply to Vishnu Balaraj

Prodigy 160 points

This is partly why I asked if TI offered an alternative driver - I'm guessing not though, as you don't mentioned any sensored solutions.

0 Vishnu Balaraj over 3 years ago in reply to Stephen Hughes1

TI__Mastermind 24415 points

Stephen,

We have MCT8316Z which is a sensored solution with trapezoidal control algorithm. Below is the link to the product page.

https://www.ti.com/product/MCT8316Z

Regards,

Vishnu

0 Stephen Hughes1 over 3 years ago in reply to Vishnu Balaraj

Prodigy 160 points

Thanks, Vishnu. One question however, I can't find anything in that datasheet which details the resolution of the PWM input to control the speed. Can this device control speed down to what is in effect 1/4000th of the motor rated speed?

Also, are there any devices where speed can be set by SPI command, rather than having to generate a very fine resolution PWM signal?

0 Andrew Liu over 3 years ago in reply to Stephen Hughes1

TI__Mastermind 18981 points

Hi Stephen,

Our team will aim to provide an updated response either by tomorrow or early/mid of next week

Thanks and Best Regards,
Andrew

0 Vishnu Balaraj over 3 years ago in reply to Stephen Hughes1

TI__Mastermind 24415 points

Stephen,

Input PWM resolution is 0.1%. Refer to the below link for more details.

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1066692/mct8316z-duty-cycle-step-resolution-needed/3946457?tisearch=e2e-sitesearch&keymatch=MCT8316Z%20PWM%20resolution#3946457

Unfortunately, we do not have any sensored devices where speed can be commanded via SPI or I2C.

Regards,

Vishnu

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MCF8316A: Very low speed control