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drv8825 - Ipeak accuracy

Bond - James Bond
Expert 5010 points
Other Parts Discussed in Thread: DRV8825

Hello Motor driver Experts,

I have a general question regarding understanding the current accuracy on the DRV8825. Data sheet shows a table of current accuracy versus

Let's look at an example:

IPeak =  Vref / (5*Resnse) = 1.5V / (8 5* 0.5 Ohm )= 600mA

Running 71% current setting resulting in the current will be 600mA * 71% +/- 5% = 426mA +/-21.3mA ( 5% of 426mA ) . Or is it 600mA+/- 30mA ( 5% of 600mA )

Would this current value contain all error sources incl. Vref tolerances and gain variations but excluding the tolerances  on Rsense?  Or how is the information in the table to be understood?

I need to be able to predict the total tolerance on the trip current..

  • 0
    TI__Expert 4435 points
    Hello Bond,

    Our experts have been notified and should reply soon. Thank you
  • 0 in reply to Luis Riveros
    TI__Expert 4650 points

    Hello 007,

    The tolerance measurement obtained in your calculations does not contain any possible errors in the VREF or RSENSE values because these are external variances.  

    Assuming you have 5% variance on your sense resistor value, this would need to be calculated in your IPEAK calculation.

    Any Variance in VREF would also need to be considered in your IPEAK calculation.

    The accuracy reported in the datasheet is the accuracy with which the driver can limit current for the different percentages of full-scale current shown in Table 2. on page 14 of the datasheet.

    The datasheet is reporting the changes in accuracy for the different percentage ranges during different microstepping levels.

    For your calculations, the 600mA * 71% +/- 5% = 426mA +/-21.3mA ( 5% of 426mA ) would be the correct interpretation.