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DRV8874: Current sense

Isee
Expert 6580 points
Part Number: DRV8874

Hi,

what if the current measurement of the driver is being set to 0.5 to 0.6A - would it still be possible to measure a change of 30mA? The goal is to be still able to measure 30mA change @ 0.67A.

Thx,

Andreas

  • 0
    TI__Guru 56650 points

    Andreas,

    If setting the current the at 0.67A, the error could be 7.5% of 0.67A. For each individual device, it may still give different IPROPI voltage with 30mA change. But, the IPROPI voltage could be same with 30mA difference on different devices.

  • 0 in reply to Wang5577
    TI__Expert 6580 points

    Hi Wang,

    We have a couple of more detailed questions - could you please take a look at:

    • How good is the resolution? Is it possible to recognize a 30mA change in current? Hence does the voltage of IPROPI ouput change if the current changes by 30mA? (indpendent of offset-error)
    • How high is the resolution of the current measurement in general? Would it be possible to recognize if there are 0.67A or 0.7A?
    • Is the current mirror scaling factor over the entire range?

    Regards

    Andreas

  • 0 in reply to Isee
    TI__Guru 56650 points

    Andreas,

    How are you going to use the 30mA resolution? Do you have a calibration system for all the boards and all the devices?

  • 0 in reply to Wang5577
    TI__Expert 6580 points

    Hi Wang, before I go back to customer could you please try to answer the questions first. Thx, Andreas

  • 0 in reply to Isee
    TI__Guru 56650 points

    Andreas,

    Resolution is different than the output error tolerance range. The DRV8874 characterization test checks the output error with few current setting points. I cannot say the 30mA resolution is good or bad.

    The current mirror scaling factor is over the entire range. But, it is a typical number.

    If they don't have a calibration system for all the parts, the 30mA resolution is smaller than the part by part error variation. So, the 30mA resolution doesn't work.

    If they do have a calibration system, please calibrate few parts to make sure the 30mA resolution work.