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DRV10983: AVS to VCC

Naizeng Wang
Expert 5460 points
Part Number: DRV10983

Hi team,

Here I find a bug of DRV10983. I use I2C input to control the speed of motor. And the relationship between I2C input and speed is shown as below.

I2C input

Speed

100

43.4Hz

200

88.6Hz

300

133.7Hz

400

177.1Hz

500

225.9Hz

 

However, when I enable the AVS to VCC function and input 100 in the box, the motor speed rushes to 234Hz, which is out of control. There is no such bug when AVS to 24V is enabled. Could you please repeat above test in lab and explain the reason. Thanks a lot!

  • 0
    TI__Mastermind 24415 points

    Hi Nison,

    Thanks for posting your question in MD forum. 

    We see this happen because Anti voltage surge (AVS) is active when AVS to VCC is chosen. When AVS is active, the speed command buffer % will be greater than  speed command %. If the BEMF voltage generated by the motor is greater than the voltage that is applied to the motor, AVS will apply a higher speed command to prevent the mechanical energy returning back to the power supply. The device buffers the speed command value and limits the resulting output voltage so that it is not less than the BEMF voltage of the motor.

    This could happen if the programmed BEMF Constant (Kt) is higher than the actual motor Kt. Can you check if your programmed Kt is correct? Please check this video if you are not sure on how to measure the motor BEMF constant Kt. 

    Another option will be to disable AVS function. We don't see this happen when AVS to 24V is chosen because AVS does not get activated when Vcc is less than or equal to 24V. 

    Regards,

    Vishnu