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DRV11873: There are some questions about this device.

Went Cao
Genius 5550 points
Part Number: DRV11873

Dear all

     I have some questions about this device, please help me to check them,thanks a lot.

     1. What is the working principle of DRV11873 device ? How to drive fan by this device ?

     2. How to achieve closed-loop control ?

     3. From 2000rpm to 260rpm speed, Is the same speed when all DRV11873 chips drive the same fan ? If not, What is the error ? Please share me with the calculate formula.

     4. What is the error between the speed of the FG pin feedback and the actual fan speed ?

  • 0
    TI__Mastermind 19720 points

    Hi,

    1. This device works by comparing the center tap voltage of the motor and comparing it to the voltage on the phase of the motor. It then uses this comparison to decide where to commutate the motor.

    2. What do you mean " How to achieve closed-loop control"?

    3. The speed of the motor should be close to the same between two different chips. I do not know this because it can depend on temperature and the process variance among the chips.

    4. There should be no error between the speed of FG and the speed of the fan because the FG speed is the speed at which the motor is commutated at. 

    Regards,

    Michael

  • 0 in reply to Michael.Walker
    Genius 5550 points

    Dear Michael

           2. In the datasheet,as below picture, it said there is Closed-loop function, so I want to know how to achieve it ?

  • 0 in reply to Went Cao
    TI__Mastermind 19720 points

    Hi, 

    Closed loop means that the motor is spinning fast enough to where the device can read the BEMF voltage and then decide where to commutate the motor. The motor will start in open loop which means the device is stepping through the commutation table in a effort to start the motor without knowing where the rotor is. Once the motor is spinning fast enough the motor driver will then transition to closed loop.

    Regards,

    Michael