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DRV10975: Motor speed control by Analog Input

Toshiro Imi
Expert 6790 points
Part Number: DRV10975

Hello,

Our customer asked about motor speed control by taking Analog Input mode on SPEED.

While he tries to change motor speed by adjusting SPEED input by analog mode, are there any restriction or limitation there, such as speed variable rate.

Best regards,

T.Imi

  • 0
    TI__Mastermind 22735 points

    Hello Toshiro-san,

    Thanks for posting to the MD forum. I am not sure I understand the question correctly here but hopefully I can answer it. In analog mode the speed pin will sample the voltage found at the speed pin input ever 320us. The voltage can range from 100mV to 2.97V, this is a linear relationship as the voltage is increased then the speed will increase as well. The speed pin acts like an ADC, sampling the voltage at certain periods which also indicates that it has a resolution, so it detects changes in the voltage of ~5.8mV.

    To put it simply if your voltage range is 2.97-100mV= 2.87V of voltage, 2.87/(5.8mV) = ~494 steps

    I hope this answers your question, if it does not feel free to rephrase the question. I hope this helps!

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    TI__Expert 6790 points

    Hi Issac-san,

    I apologize for a confusion. I am wondering what the customer needs to know was cautions to consider if he changes the motor speed in analog mode, something like acoustic noise will be happened or damaging to the motor if he changes the motor speed quickly.

    Anyway, I will feedback to the customer your suggestion and try to know what is his concern.

    best regards,

  • 0 in reply to Toshiro Imi
    TI__Mastermind 22735 points

    Hello Toshiro-san,

    No worries just trying to get you the answers you are looking for. This device actually has a closed loop acceleration feature so the user can define the ramp up speed of the device. So if they increase the analog voltage on the speed pin, they can set it to slowly increase until it gets to the target value. As far as acoustic noise goes there is a possibility of noise if the acceleration speed is extremely fast. For example if going from 1000RPM and the device is set to go to 5000RPM with a very high acceleration rate then there will definitely be audible acoustic noise.

    Best,

    Isaac