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DRV8313 Output Current Specification

Kevin Holm-Hansen
Prodigy 40 points
Other Parts Discussed in Thread: DRV8313

I am considering utilizing the DRV8313 in a new design. I need to understand at what point will the 8313 detect an overcurrent at various temperatures. The targeted maximum drive current for the BLDC motor is presently not finalized, but is in the range of 1.5 to 2A. The data sheet description for the 8313 mentions a 2.5A peak or 1.75A rms maximum current at 24V and 25 C. The electrical characteristics table lists the Over Current Trip level as 3A minimum at 25 C. I assume that this equates to a voltage level on a comparator that is determined by the FET resistance and winding current (3A * 0.24 Ohms = 0.72V). So that at increased temperatures the FET resistance goes up and the overcurrent trip level would decrease proportionally.  

I am planning on applying PWM waveforms to the 8313 to control the winding current. The PWM frequency will be selected with the motor inductance and resistance in mind to provide a known ripple current.

 

My Questions are;

  1. Are my assumptions correct?
  2. Can I use the values of PWM frequency, motor inductance, resistance, FET on resistance and Temperature coefficient, and derived overcurrent threshold voltage to determine the over current trip point for a certain set of values?

Thanks,

Kevin  

  • 0
    TI__Expert 8885 points

    Kevin,

    Let me investigate with designer. I will get back to you as soon as possible.

    Best Regards

    Milan

  • 0 in reply to Milan Rajne
    TI__Expert 8885 points

    Kevin,

    3A is absolute minimum threshold valid across whole temperature range i.e. device is guaranteed not to insert nfault till 3A current.

    Your understanding is correct that as temperature rises, threshold will reduce due to I increase in FET’s RDS-on.

    The answer to your second question is not easy and straight forward because even though trip threshold depends upon all the variables you mentioned, it’s not linearly related to them and will vary significantly from device to device, therefore as worst case 3Amp is defined in data-sheet.

    Best Regards

    Milan