MCF8316A: SPEED_FDBK register usage

Kamesh Durvasula

Part Number: MCF8316A

Hi,

I want to use the SPEED_FDBK register, but its not obvious to me what are the final units of the calculated speed given the equation in the register description. Probably rotations per minute, but I would like to be sure.

Many of the conversion formulas use "base current":

iBus = (BUS_CURRENT / 227) * Base_Current/8

But Base_Current is never explicitly defined.

Any help is apprecaited.

Thanks in advance,

kamesh

over 3 years ago

0 Eric Chen over 3 years ago

TI__Genius 9220 points

Hi Kamesh,

Thanks for your posting your question and feedback to the MD forum.

The end unit of the estimated rotor is in Hz after using the conversion equation. There's actually an error here in the datasheet, and the SPEED_FDBK register formula should be:

estimatedSpeed = (SPEED_FDBK / 2^27)*MAX_SPEED (Hz)

Regarding the base_current, I'm checking this with our design team, and I'll get back to you as soon as possible.

Thanks,
Eric C.

0 Kamesh Durvasula over 3 years ago in reply to Eric Chen

Prodigy 155 points

Thanks for your reply Eric. We are trying to setup the FW. But we are still unable to use the Eval kit to get the motor rotating.

Any help in this regard will be helpful.

Thanks,

Kamesh

0 Kamesh Durvasula over 3 years ago in reply to Eric Chen

Prodigy 155 points

Hi Eric,

Is there a way we can get in touch on a conference call?

We are working on a time critical project and any help is appreciated.

Thanks

Kamesh

+1 Eric Chen over 3 years ago in reply to Kamesh Durvasula

TI__Genius 9220 points

Hi Kamesh,

Sure, I'll connect with you privately.

Regards,
Eric C.

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MCF8316A: SPEED_FDBK register usage