DRV8461: Coil Current Calculation

Marco Rojas

Part Number: DRV8461

Hi team,

I have a customer with the below question. Let me know what you think and thanks in advance for your help!

"Please explain how to use DRV8461 INDEX4/INDEX5 registers to calculate coil A current. What current in amps does the maximum register reading of 1023 represent?"

Marco

over 1 year ago

0 Murugavel4637 over 1 year ago

TI__Mastermind 32365 points

Hi Marco,

The INDEX4/INDEX5 registers output the coil A current magnitude scaler. 1023 corresponds to 100% of the full-scale current setting. 0 to 1023 corresponds to 0 to 100%.

Regards, Murugavel

0 Marco Rojas over 1 year ago in reply to Murugavel4637

TI__Intellectual 2270 points

Hi Murugavel,

Thanks for the reply. I have the customer response below

"I am running the motor at constant speed with a full scale current of 0.5A (sine waveform). I get different coil A readings every time I read the registers. Shouldn’t the readings be 0.5A all the time?"

Marco

0 Murugavel4637 over 1 year ago in reply to Marco Rojas

TI__Mastermind 32365 points

Hi Marco,

This is the current reading at the indexer position of current A from INDEX3 (polarity of current indicated in INDEX2). The percentage of currents for each indexer positions is given in a tables 7-7 to 7-9 in the datasheet https://www.ti.com/lit/ds/symlink/drv8461.pdf pages 21-23. As the STEP inputs keep advancing the indexer the current keeps changing. The INDEX4/5 registers provide instantaneous output current magnitude. So it will keep changing as per the table.

Regards, Murugavel

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DRV8461: Coil Current Calculation