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DRV11873: DRV11873 speed overshoot at start up

Rudnik
Intellectual 350 points
Part Number: DRV11873

Hello,

I have successfully gotten the DRV11873 running with a hard drive motor. My PWM is 28 KHz and I run it at 12 V. The current resistor is 1 K and in lowspeed.

The problem is when the device is powered up I put a ramp on the PWM. But the DRV spinns up the motor to a high speed and then regulates down to the PWM supposed speed. My duty cycle is just about 6 %.

How can correct this or this or is this device related behavior? I already tried other voltages but there is no difference. 

Thanks!

Best regards

  • 0
    TI__Expert 6065 points
    1) Try changing FS pin between the high speed and low speed motor settings. One setting may help alleviate this problem
    2) Try using the CS pin to limit the current and thus limit this high speed
  • 0 in reply to Sanmesh Udhayakumar
    Intellectual 350 points
    Hi,
    sorry for the delay. I just used the CS resistor as in the datasheet. Changing it to 5K did the trick. It seems obvious now, first I thought the value was mandatory.
    Typical case of did-not-reed-the-datasheet-properly. Shame on me, thanks to you. Guess I was a bit to quick and careless about it.