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Difference between IFs. IOCP, Itrip and Ichop

Hadi Kalani
Prodigy 120 points
Other Parts Discussed in Thread: DRV8711

Dear friends

I was reading Drv8711 to adjust registers. But I can not distiguish currents such as  IFs. IOCP, Itrip and Ichop.

Please help me to understand them better.

Thanks

  • 0
    TI__Guru** 114905 points
    Hi Hadi,

    IFs is the maximum amount of current through the winding:

    From section 8.2.2.2 the set full-scale current (IFS) is the maximum current driven through either winding.

    IOCP is the maximum current allowed in the system in the event of an unexpected event. For example, if a winding is shorted too much current may flow through the FETs. By setting the maximum Vds voltage, the DRV8711 will report a fault.

    Itrip and Ichop are the same. It is the percentage of IFS current that is being regulated at each step.
  • 0 in reply to Rick Duncan
    Prodigy 120 points
    Dear Rick
    Thanks for your answer. I have two another questions:
    1- But in DRV8711, we are able change IFs but i dont find a way to vary other current such as Itrip. How can I define it?
    2- If we want to drive a Stepper motor with 6A, what value is must be chosen for IFs?
    Thanks
  • 0 in reply to Hadi Kalani
    TI__Guru** 114905 points
    Hi Hadi,

    My apologies. IFS and ICHOP are the same. Itrip is a percentage of IFS/ICHOP

    1 - Please refer to Table 4 of the datasheet. Itrip is a percentage of IFS based on this table.
    2 - Please refer to Equation 1. To obtain 6A, the TORQUE, ISGAIN and Risense are used.
  • 0 in reply to Rick Duncan
    Prodigy 120 points
    Dear Rick

    1-You mean that the value in Table 4 are Itrip?
    2- We used a current prob to see the stepper phase current winding. but I want to know, what are the differences between this current and AOUT or BOUT current (aspect of frequency, amplitude)? . Are they the same current?

    Thanks
    Hadi
  • 0 in reply to Hadi Kalani
    TI__Guru** 114905 points
    Hi Hadi,

    1) The values in Table 4 are Itrip percentages of IFS.

    For example, if IFS is set to 5A step 5 of 1/8 step will regulate the current to approximately 3.55A (71%) in the A coil.

    2) The stepper phase current is the same as the Itrip current. This current can vary somewhat depending on the decay mode, off time, blanking time.

    For more information, see the DRV8711 Decay Mode setting and Optimization and DRV8711 Quick Spin and Tuning Guide. The links can be found in section 11.1.1 of the datasheet.