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The full-scale (100%) chopping current setting of DRV8880

user4530078
Prodigy 120 points

Dear Motor support team,

I set the IFS to be 2.0A maximum peak current with 3.3V Vref,  250*10^-3ohm Rsens and 100% TRQ setting.

I confirmed IFS setting with P.18 in www.ti.com/.../drv8880.pdf.

However I observed about 1.4A peak current at 800pps and 1.17A  at 3000pps respectively.

Why I can not obtain 2.0A peak current in this conditions?

Please confirm the attached file.

Yohjiro Kawai,

Peak Current Observation.pdf

 

  • 0
    TI__Guru** 114905 points

    Hi Kawai-san,

    Are you using full step? If so, the current will be 71% of the IFS value.

    If you are using half step or higher levels of microstepping, the current should reach the IFS setting at lower speeds. At higher speeds, the current may not reach the desired level.

    What are the motor specificiations?

    What is the VM voltage?

  • 0 in reply to Rick Duncan
    Prodigy 120 points

     Hi Rick,


     Thanks for your reply and I am very sorry to miss reading of the manual regarding Microstepping setting in Table1.

    Now I confirmed 2.0A peak current with half step mode at 1000pps and 3000pps as seen in the attached file.

    (Basically, the motor current rating is 1.4A/φ, in this time, I raised the current up to 2.0A in an aim to boost the torque for the heavy load. Druing the motor is stopping, the current is reduced to 1/4 by the torque contoroll to supress the heating on the driver and the motor.)

    However, I was wondering why does the current to be dumped by 1/root(2) at Full step mode?

    Yohjiro,Peak Current Observation II.pdf

  • 0 in reply to user4530078
    TI__Guru** 114905 points

    Hi Yohjiro,

    The device is designed to provide the same RMS current using full step or microstepping.

    The RMS current of a microstepping sine wave is 1/root(2) or 70.7% of the IFS setting, and the RMS current of a full step wave is also 71% of the IFS setting.