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DRV10987: DRV10987 : Reading Current (0x04) and Voltage (0x05) from register

Pradyumna Jena19
Prodigy 10 points
Part Number: DRV10987

Hi,

I am reading both current and voltage from DRV for monitoring in a ceiling fan application.

Value read from voltage read of DRV, converted as mentioned in datasheet.

Although the value is fluctuating, still it is useful to application.

But, the converted value of current is not at all matching with reading with a Fluke-115 DMM (True RMS),

The conversion formula mentioned in datasheet is A = 3 * (Register Value - 1023)/ 2048.

Register value is 11 bits value.

Can anyone help me out?

regards

PK JENA

  • 0
    TI__Expert 6065 points
    Hey Pradyumna,

    Let me confirm on monday when we are back in office.

    Sincerely,
    Sanmesh U.
  • 0 in reply to Sanmesh Udhayakumar
    TI__Expert 6065 points

    Hey Pradyumna,

    Please give us the week to verify on the bench this motor current equation.

    We know that the current register refers to the motor phase current. We just want to verify that the equation is correct for calculation.


    Sincerely,
    Sanmesh U.

  • 0 in reply to Sanmesh Udhayakumar
    TI__Expert 6065 points
    Hey Pradyumna,

    The current register refers to the amplitude of the motor phase current.
    we are still verifying what the proper equation is, but we think it is the below:
    if MotorCurrent[10:0] >=1023
    Current (A) = 3 × (MotorCurrent[10:0] – 1023) / 512
    Else
    Current (A) = 3 × (MotorCurrent[10:0]) / 512
    We have seen that this is fairly accurate when the phase current sinusoidal signal is clean and constant peak, but is less accurate when the signal is less sinusoidal if you are improperly spinning the motor. Thus it can only give you an estimate of what the amplitude of the motor phase current is and might not be accurate all the time.

    We will be doing more investigation on the reliability of the current register but this is what we have so far.

    Sincerely,
    Sanmesh U.