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DRV5011: I want to use DRV5011 with power saving.

Part Number: DRV5011

We are considering the DRV5011 to replace the AK8771 manufactured by Asahi Kasei.
The AK8771 has a power down pin for power saving drive, but the DRV5011 does not.
Therefore, we are considering using the DRV5011's VCC power supply for on/off control.
Therefore, we are considering using the DRV5011's VCC power supply for on/off control. Is this kind of usage acceptable?
Also, when the magnetic flux density is between BOP and BRP, what will happen to the output when the power is turned on?

Thank you very much.

  • Fukasawa-san,

    It is acceptable to switch VCC on and off for power savings with DRV5011.  However, it is important to keep in mind that there is a power on time that must be satisfied before the output is sampled.  For this device the maximum specification is 70 us.  

    In the event of a power on when the input is between BRP and BOP (i.e. 0 mT), the device should default to the release state after the on time is satisfied.

    Thank you,

    Scott

  • Mr. Scott.

    Thank you for your answer.
    I understand that it is possible to control ON/OFF.

    Am I correct in understanding that if the magnetic flux density is between BRP and BOP, an invalid value will be output immediately after power-on?

    I plan to use the DRV5011 to detect the rotational position of a BLDC motor.
    If the rotor position stops between BRP and BOP, the DRV5011 will not be able to detect the exact rotor position when it restarts.
    In this case, does it mean that I need to rotate the motor until the magnetic flux density exceeds the threshold to output a valid value?

    Best regard.

  • Regardless of the input state, there is always an uncertainty in the output until Ton duration is completed.  

    After this time, there are two cases for an input which is between BRP and BOP.  In the event that the input field had been below BRP before, then there is no error to the output state after power is restored.  However, if the previous state had been BOP, then the device will power on and determine that there is not sufficient field to trigger again.  This would result with a temporary uncertainty of position for a single sensor.  However, what is common in BLDC motors is to use 3 sensors each placed 120 degrees separated.  You can find more information on the configuration in the video linked below

    https://training.ti.com/kr/ti-precision-labs-motor-drives-commutation-trapezoidal

  • Mr. Scott.

    Thank you for your answer.
    I interpreted it as the need to perform compensation control based on the rotational position before stopping, in case some of the three Hall sensors of the BLDC motor had indefinite output.

    Thank you for your cooperation.