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DRV2624: The accuracy of DRV2624 Driving Time

Part Number: DRV2624

Hi TI,

1.Do you have the tolerance of driving time like one cycle or half cycle? We find the waveform is different if we drive a very shot time like 2~8ms.(Vibrator operation frequency is 170Hz)

  • Hi Eddie,

    What do you mean like one cycle or half cycle? Could you explain a bit further what you want to know?
    The actuator takes some time to startup, and also to brake. There are several plots in the device data sheet that show output drive and acceleration over time. In addition the closed-loop mode use over-drive for accelerated startup and braking.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • Hi Ivan,

    Correct my question.
    My question is we're using open loop to drive our vibrator now,and also enable auto-break for breaking.
    1.As I know, when using auto-break,DRV2624 will change to closed loop to break the vibrator, but since we use open loop(170Hz),the break frequency(maybe 160Hz) will not the same with operation frequency, is this will cause any problem like increase the breaking time or some side effect?

    2.What time does DRV2624 need for start-up and breaking?

    3.Attach photo is using the same DRV2624 with same vibrator but the result show the different breaking pattern, is it a normal behavior?

  • Hi Eddie,

    Have you run the calibration for the actuator?
    Figures on section 8.6.9.4.1.1 show how the auto-braking is performed depending on the operation mode. Also Figures 10 and 11 show braking effect and timing.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • Hi Ivan,

    Yes I have run auto calibration.
    So is the waveform I measure is a normal behavior?
    Can we change auto-break voltage by register?
    And from 8.6.9.4.1.1 ,Does it mean it will takes 50ms to auto-break?
  • Hi Eddie,

    Yes, at least the first part of the braking looks consistent across the three tests, although there seems to be some small variation at the very end.
    About the auto-break time, that would be the spec, the plots from figure 10 and 11 show around 20ms.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • Hi Ivan,

    We observe a waveform that when we enable two vibration which are 25ms with 0.9v(OD_LCAMP) and 10ms with 1.8v(OD_CLAMP), I found the auto-break use the same voltage(1.8v) for breaking.And I have some questions of this behavior:
    1.Can we change the auto-break voltage?
    2.What is the best voltage for the breaking?
    3.If auto-break change to closed loop,do we need to set register 0x1f(RATED_VOLTAGE)?If yes,what value should we set?
    4.What is the driving time tolerance?
  • Eddie,

    1. Auto-brake should be performed at the OD_CLAMP voltage. What is your FB_BRAKE_FACTOR setting? When you run the calibration, what are the values you write into the device?
    2. The peak voltage from the actuator spec would be the best for braking. Regarding auto-brake, It is mentioned in the data sheet that a brake factor of 3 is valid for most actuators
    3. As mentioned in the data sheet: To use the automatic braking feature, the device must be configured appropriately for closed-loop operation. So closed-loop settings and calibration must be run.
    4. Based on data sheet captures it would be 50ms although some of the typical characteristic plots show around 20ms.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • Hi Ivan,

    Thank you for you reply!
    Another question about vibrator resonance frequency(f0), what is the accuracy of DRV2624 auto-calibration for f0?
    And is there factor will affect vibrator f0 shift or variation?
  • Hi Eddie,

    The algorithm ensures that drive frequency is within 2Hz of the resonance frequency.
    Resonance frequency may vary from part to part, based on manufacturer tolerance. Also aging may affect the resonance frequency.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • Hi Ivan,

    We have a issue on the device that when we enable two vibration which are 25ms with 0.9v(OD_LCAMP) and 10ms with 1.8v(OD_CLAMP) in sequence mode, and there is 100ms between this two vibration.It can't stop the vibration after the first vibration

    From PWM waveform,the DRV2624 is keep doing breaking during the 100ms, is there any clue we can check on this issue?or any factor cause this issue?

  • Eddie,

    It seems like the feedback value from the actuator is not letting the device know that the actuator is stopped.
    Does this happens only for this specific combination? Does this happens randomly or every time the sequence is ran.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators