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DRV2667: Help driving Powerhap actuator

robin harvey
Prodigy 60 points
Part Number: DRV2667

Hi,

I am designing a miniaturized device with a single multi-layer actuator called PowerHap the 12.7mm or 7G version, designed by TDK.

Since these actuators seem to be the first of their kind I was wondering if anyone has already tried driving them with this chip.

They have a capacitance of 1uf and can be driven to a maximum of 120v.

I am aware that the DRV2667 struggles with this as it is stated that it can only drive a 1uf load to 40vpp at 300HZ, however I do not have space for a less integrated driver therefore I am using this chip.

I was wondering about what external components it will work best with, or any other advice from someone who has already tried this.

Best regards,

Rob

  • 0
    TI__Intellectual 1910 points

    Hey Robin,

    Thank you for your interest in our products. We have tested the 7G actuator from TDK with the DRV2667EVM-CT. The DRV2667 experiences a drop in boost voltage from the large capacitance, but it is still able to drive the piezo sufficiently. A good place to start is to look at section 8.2 in the datasheet, Typical Application, that shows the external components to achieve maximum output voltage.

    It is also worth taking a look at the DRV2667EVM-CT which discusses external component selection in section 3.6 of its user guide.  With the EVM, you can connect the actuator and try different waveforms either externally or through Haptic Control Console to judge performance at different gain settings.  

  • 0 in reply to Micah B Brouwer
    Prodigy 60 points

    Hi,

    Thank you for the quick reply, I'm using the actuator to simulate tactile switches so is simply playing a square waveform at full scale going to give the strongest tactile response, however I was curious whether there's any difference in it's drive ability for a single rising edge vs a continuous sustained square wave.

    Also did you drive the powerhap negatively? it seems from the datasheet that it is only meant to be driven one way unless I'm mistaken.

    Regards,

    Rob

  • 0 in reply to robin harvey
    Prodigy 60 points
    HI,

    I'm still wondering how you drove the powerhap, as it seems that its only possible to drive the power-hap positively using direct wave forms on the drv2667 which is not optimal, so did you manage to drive it negatively or else are there any better ways of making the drv2667 function single ended?

    regards,

    Rob
  • 0 in reply to robin harvey
    TI__Intellectual 1910 points
    Hey Rob,

    Briefly stated, as the minimum voltage in the powerhap's datasheet is 0V, I don't think the actuator should be driven differentially. To drive it with single-ended output, just ground one of the terminals. To your first question about how to achieve the best response:

    If you are simulating a tactile switch, a single rising edge will not displace the piezo enough for the user to notice. You are correct, a full scale waveform will give the strongest tactile response. I recommend using the WaveSynthesizer tool on Haptic Control Console with the DRV2667EVM-CT, which allows you to build and test different waveforms.
  • 0 in reply to Micah B Brouwer
    Prodigy 60 points
    Hi, thank you for the advice I have tested the example waveforms from the datasheet and can confirm that it now works.
    Regards,
    Rob