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DRV8323: Current limit of the H Bridge

Shivaraja Narayanappa
Prodigy 120 points
Part Number: DRV8323

Hi,

I am using DRV8323HRAR for driving a BLDC motor, configured the Driver with 6PWM mode by connecting the MODE pin to the Ground. IDRIVE is open so that the gate current can be 120mA. Attached is the schematic of the driver.

I am using the MOSFET with part number FDD8896 who's RDS on is 6.8m ohm at VGS of 10V.

Now i have connected an 18K resistor between VDS and DVDD, in this case the current limit to the motor was suppose to be 289Amps(1.88V/6.5m ohm). But the motor consumes on 2Amps of current in this case.

To cross check my other hardware, i have connected DVDD to the VDS, in this case the motor runs fine without any problems. and maximum current is also consumed. But i am worried in case of the Motor Jam the MOSFET will damage because of too much current.

Kindly let me know what i am missing to limit the current.

Looking forward for your support.

Best Regards,

Shivaraja.N

  • 0
    TI__Guru** 114905 points
    Hi Shivaraja,

    Our expert has been contacted and should reply by Friday.
  • 0 in reply to Rick Duncan
    TI__Expert 8985 points

    Hi Shivaraj,


    Now, I see that you have two test situations: one with Vds monitored at 1.88 V, and one without monitoring.

    Now, if you operate with Vds monitored at 1.88 V but the current you measured does not match the voltage and Rds on basec current calculation, you might need to check how you measure the current. Is it power supply base measurement? We recommend you current probe the motor, get the Rsense voltage and find the current on the sense resistor, or directly measure the Vds voltage to see if they match with your calculations.

    The way we recommend you limit the current is by Vds monitoring or by Vsen_ocp tripping. on HW device, the Vsen_ocp trip value is 1 V. Vds monitoring is set as you have done.