DRV10987: Issue with start up settings

Hello Amit,

I have a few questions:

1. Can you run the motor at the target RPM?
   1. Regardless of the time it takes to reach the target RPM
2. Have you verified that the Phase Resistance and Kt values were correctly measured?
   
   1. View online here
3. Is the customer not concerned with the built in device protection that can monitor for motor locks? (e.g. BEMF Abnormal, Speed Abnormal, Current Limit)
   
   1. If they are, they should renable these locks by clicking the checkboxes in the Lock Detect section on the Advanced Settings tab. This include the Mechanical AVS enable

Let me add the recommendations below:

• Generally speaking, there is a trade off between fast start up time and a reliable start up. Trying to start up to fast will result in a higher chance for the motor to not start up correctly
  • As a result, the motor parameters (Kt, phase resistance, and Tcontrol) should be tuned perfectly so we can rule out the possibility of them causing a problem
• Speeding up open loop behavior can decrease the start up time. Decreasing Align Time, Open to Closed Loop Threshold, and Increasing the First and Second Order Acceleration constants will help decrease start up
  
  • With that said, Open loop behavior is largest factor if the motor start up successfully, remember the tradeoff
• The closed loop acceleration (and current limit, which you have disabled) is what determines how fast the motor will reach target RPM speed after the device has transitioned into closed loop (i.e. able to change speed command and the motor responds).
• Please follow the Guidelines in the DRV10987 Tuning Guide for PWM Output and Slew Rate Options (120V/us = 440ns)
• If the phase resistance is that small (<1ohm), I suggest evaluating if doubling the PWM frequency helps

If you have not seen it yet, the DRV10987 Tuning guide should be able to help you tune further.

Best,

-Cole