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MSP430F5521: Max RPM specified in App note SLAA503 July 2011

Suresh leley
Prodigy 160 points
Part Number: MSP430F5521


The application note Sensored 3-Phase BLDC Motor Controller Using MSP430 specifies maximum speed as 41000 rpm for Hurst DMA0102024C 6 pole motor -sec 2.3.2 Page 9, foot note 2. Could you please explain how this value is calculated? Assuming a 8.125 us hall interrupt even processing time I am getting a factor of 10 error.

  • 0
    TI__Expert 4110 points

    Hi,

    I believe you can find below info in the application note in page 11, the "1/MAX_HALL_ISRs_1SEC" which equals to 8.125 us, and "NUM_MOTOR_POLES" = 6, since that you can get the "MAX_MECH_SPEED_IN_RPM" value equals to 41000 rpm.

    Best Regards,
    Peter

  • 0 in reply to Peter Jiang
    Prodigy 160 points

    Thanks Peter,

    using the formula for 6 pole motor running at 41000 rpm,  MAX_HALL_ISRs_1SEC =

    (41000/60)(3*6) = 12300.

    Then the time available for ISR Processing = 1/12300 = 81.3 us and not 8.13 us or 8.125 us as stated in the App note.

  • +1 in reply to Suresh leley
    TI__Expert 4110 points

    Hi Suresh,

    I believe you are right, there is a mistake in this app note, I will report to the team to see we can update in the future, thanks for pointing out and also sorry for making you confused.

    Thanks!

    Best Regards,
    Peter

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