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MCF8329EVM: HW_LOCK_ILIMIT

TATSU Numa
Intellectual 800 points
Part Number: MCF8329EVM

Hi Team

 Let me ask about HW_LOCK_ILIMIT.

When the cosutomer increase load to motor  while the motor is spinning, an HW_LOCK_LIMIT error will occur.

There are two formulas for calculating base current depending on the data sheet:
①Base Current in Ampere = 1/5(RSENSE x CSA_GAIN)
②BASE_CURRENT = Base Current in Ampere x 32768/1200

When setting RSENSE = 1mΩ, CSA_GAIN = 20V/V, BASE_CURRENT=0x400
Base current = 75A due to ①
Base current = 37.5A due to ②

Which calculation formula should customer use in this case?

best regards

TATSU

  • 0
    TI__Genius 12215 points

    Hi TATSU,

    The value in the BASE_CURRENT register is a user set value which sets the max measurable current by the internal CSA. To determine the correct BASE_CURRENT value to set first use equation 1, 1/5(RSENSE x CSA_GAIN), to determine values for RSENSE and CSA_GAIN that result in a current value that is slightly above the motors rated max peak current. Once a good value for RSENSE and CSA_GAIN are determined, then use the equation 1/5(RSENSE x CSA_GAIN) x 32768/1200 to find the value to program into the BASE_CURRENT register, just make sure to convert this value into hex.

    Regards,

    Joshua