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DRV8889-Q1: DRV8889-Q1

Lakshmi Teja Gedela
Prodigy 90 points
Part Number: DRV8889-Q1

Hi Team,

In our driver datasheet, in table 8-2 we have observed two half stepping modes as( non-circular half step mode and half step mode), could you please explain what is the main difference between those two modes?

Please let us know in your earlier convenience.

Thank you 

  • 0
    Prodigy 20 points

    Hello, here is the table for comparison:

    Step

    1/2 step

    A and B motor coils currents

    1/2 step non-circular

    A and B motor coils currents
    1 0%, 100% 0%, 100%
    2 71%, 71% 100%, 100%
    3 100%, 0% 100%, 0%
    4 71%, -71% 100%, -100%
    5 0%, -100% 0%, -100%
    6 -71%, -71% -100%, -100%
    7 -100%, 0% -100%, 0%
    8 -71%, 71% -100%, 100%

    In the table are A and B motor coil currents. If we assume that motor coil has resistance R then you can calculate a power consumption of the motor for each step like:

    P = R * I_A^2 + R * I_B^2

    When you calculate power for each step of 1/2 step mode (circular):

    R * 100% * 100% = R * 100% (valid for steps 1, 3, 5, 7)

    R * 71% * 71% + R * 71% * 71% = R * 50% + R * 50% = R * 100% (valid for steps 2, 4, 6, 8)

    It means that in "circular" mode the power consumption is the same at each step.

    But for non-circular mode:

    R * 100% * 100% = R * 100% (valid for steps 1, 3, 5, 7)

    R * 100% * 100% + R * 100% * 100% = 2 * R * 100% (valid for steps 2, 4, 6, 8)

    Power consumption is double each second step. This helps the motor to stay synchronous in higher RPM but the torque fluctuates more.

    These calculations are valid only for very low RPMs because the coil inductances can be ignored.