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DRV10983: Several questions

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Replies: 1

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Part Number: DRV10983

Hi all

Would you mind if we ask DRV10983?

<Question1>
Is it possible to configure Abnormal speed's threshold?
We are sorry that we could understand it.

<Question2>
How much is the maximum speed?
It shows at 8.4.11.2 Motor Speed Readback, right?

Kind regards,

Hirotaka Matsumoto

  • Hello Matsumoto-san,

    An expert has been notified and will reply to followup questions as needed. Let me try to address 

    <Question1> Is it possible to configure Abnormal speed's threshold? We are sorry that we could understand it.

    You're completely fine, we get questions on locks all the time. The threshold of the abnormal speed is dynamic. Its entire function is to prevent a motor BEMF (BEMF2 in the datasheet) that is larger than the applied voltage (V_U in the datasheet). If motor BEMF is greater than the applied voltage, then motor current will flow through the body diodes and into the supply voltage, which could cause a voltage surge on the supply. The most common way for BEMF to be greater than the supply voltage is when an external force causes the motor to spin faster than we are driving the motor (spinning faster than expected = abnormal speed).

    Because the motor's BEMF constant, Ke or Kt, is equal to the Back EMF divided by motor speed (Kt = BEMF2/Speed), we can measure Speed and use the programmed Kt to determine how much BEMF will be produced. In addition, we can use the motor model theory (V_U = I*R + BEMF1) to measure the current and use the programmed resistance and applied voltage to calculate BEMF again. So, you could influence the threshold by purposely programming incorrect resistance and Kt but I assume you don't want to do that.

    Again, the purpose of the abnormal speed is not program a speed that the driver cannot exceed. Abnormal Speed is to ensure that motor BEMF is not larger than the applied voltage.

    <Question2> How much is the maximum speed? It shows at 8.4.11.2 Motor Speed Readback, right

    8.4.11.2 shows the largest read speed by the device. I will say that Table 10. Recommended Application Range shows the maximum operating closed loop speed (or output speed) = 1000Hz which is less than maximum read speed. I will say, I have seen some motors push above 1000Hz but the recommended application table shows that we lose confidence in our algorithm and device hardware if this range is exceeded.

    Best,

    -Cole