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DRV8832-Q1: Vset to control duty cycle?

Kevin Schmidgall
Expert 3270 points
Part Number: DRV8832-Q1

Hello,

We are currently running the DRV8832-Q1 at 100% Duty Cycle.

We would like to look at running it at a PWM frequency above the audible range (25-30kHz)

The datasheet states a 12ms ramp time when IN1 or IN2 is pulled high, limiting us to around 25Hz.

Can a PWM filtered to a DC voltage be fed to Vset to control the duty cycle?

Regards,

Kevin

  • 0
    TI__Expert 3270 points
    This was a question from a customer. I think I get what they are getting at...if you are at 100% duty cycle then you should be able to decrease the regulated voltage to get it back to a duty cycle that is less than 100% but I dont know what the effect of that would be. Just worse motor performance?

    Regards,
    Kevin
  • 0 in reply to Kevin Schmidgall
    TI__Expert 3270 points
    Now that I have looked into it even further it looks like they may be confused by the datasheet:

    The only place I found 12ms mentioned is in 7.3.2 "This can take up to 12ms to go from sleep to 100% duty cycle". I think he is taking that to mean that that is how fast the PWM is running. But to me, after reading it, that just means that once you go from sleep to Rev/For it will take 12ms to get back to normal operation. The part works at a 44.5kHz typical PWM frequency. Is that correct?
  • 0 in reply to Kevin Schmidgall
    TI__Guru** 114905 points
    Hi Kevin,

    You are correct. The device will PWM the outputs at ~44.5kHz.

    When exiting sleep, the duty cycle is low and increases until the motor voltage matches the voltage set by VSET.

    VSET can be adjusted while the motor is running, but there will be some delay before the motor meets the new target voltage due to the integrator shown in the functional block diagram.