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TMAG6180-Q1: absolute position at power-on

Jade Lan
Prodigy 260 points
Part Number: TMAG6180-Q1
Other Parts Discussed in Thread: ADS9326, ADS8354

Tool/software:

Hi team,

The customer has the following two questions to confirm.

1. Is the method for obtaining the absolute position at power-on based on zeroing, obtaining the offset between the magnetic field zero point and the mechanical zero point, and then finding the specific sector based on Q0 and Q1, and combining sin/cos to obtain the specific mechanical angle information?

2. Is there any application documentation on motor zeroing and obtaining absolute position at power-up? Could you provide it?

Best Regards,

Jade

  • 0
    TI__Mastermind 21060 points

    Jade,

    To determine the absolute position, the system would need to capture SIN and COS.  This can be done using a differential to single ended stage or by using a differential input ADC (like ADS8354 or ADS9326).  The result of that conversion is used in an arctangent calculation.  The resulting angle will correspond to two possible rotation angles. 

    Next the Q0 and Q1 outputs are read to provide quadrant information.  Together they provide 4 unique output states per revolution.  Both are needed to ensure no uncertainty near zero crossings.

    The result of this combining these two readings will produce a unique output for any given rotation angle of the magnet, but there may still be some angle offset.  This would be related to how well the magnet is aligned to the actual system.  This would require a one time zeroing calibration to determine what the effective difference is between the electrical 0° and the mechanical 0°.

    Thanks,

    Scott

  • 0 in reply to Scott Bryson
    TI__Prodigy 260 points

    Hi Scott,

    Thank you for your answer.

    Do you have any application documentation available on motor zeroing and absolute position acquisition at power-up?

    Regards,

    Jade

  • 0 in reply to Jade Lan
    TI__Mastermind 21060 points

    Jade,

    We only have this calibration document:

    https://www.ti.com/lit/an/slya085/slya085.pdf

    It covers most of the corrections that might need to be done to the AMR signal, but I don't think it addresses when the magnet is not aligned mechanically to 0°.