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DRV8350H-EVM: Overcurrent Fault

GAGANDIP SINGH DADHWAL
Prodigy 155 points
Part Number: DRV8350H-EVM
Other Parts Discussed in Thread: MSP430F5529, DRV8350, DRV8350S-EVM

Dear TI Team,

I am trying to control a BLDC Motor using DRV8350H-EVM in sensored operation. But as soon as I increase my Motor Speed over 50%, my motor stops and an Overcurrent Fault is triggered in the DRV8350x EVM GUI Software.

Below are the specifications of motor:

  1. No. of Pole Pairs : 8 Pairs
  2. Max peak current: 10A
  3. Operating Voltage: 24V
  4. Hall Sensors: 3 (120deg)
  5. Nominal Current:25A
  6. Power: 150W

Steps performed:

  1. Flashed the EVM, with Sensored Firmware Provided by TI, installed in the following path: C:\ti\DRV8350x_EVM_BLDC_FW_1.0.0\DRV8350x_EVM_FW\DRV8350x_EVM_BLDC_FW_1.0.0\DRV835X_MSP430F5529_Trapezoidal_Sensored_BLDC.
  1. Connected to DRV8350x EVM GUI Software and tried to control motor speed.

Observations:

  1. Initially, the overcurrent fault was triggered as soon as we tried to increase the motor speed over 20%. Increasing the PWM Switching Frequency from 25kHz to 60kHz (maximum) helped in increasing the Motor Speed upto 50%.
  1. As per the documentation available, MOTOR_PHASE_CURRENT_LIMIT is the parameter that triggers over-current fault. The default value of this parameter in the firmware is 900.


    Considering the above formula,

    MOTOR_PHASE_CURRENT_LIMIT = 900;

    CSA = 5V/V

    We get amperes as 20.71 A.

     My motor has peak current of 10A. So ideally with these settings I should not get an overcurrent fault.

  2. We were unable to verify the value of the current sense amplifier (CSA) from the Hardware. Also, from the documentation below, it was inferred that the DRV8350-H must have 4 pins, GAIN, IDRIVE, MODE & VDS

       

        4. But in the schematic, I am unable to find the GAIN pin

             

        5. As per my understanding this GAIN pin is required to set/read the value of CSA as shown below:

         

        6. Kindly help us identify the actual reason for this overcurrent fault so that we can run the motor at its full RPM.

       Thanks & Regards

       Gagandip Singh Dadhwal