• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 29 subscribers
  • Views 845 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV2667: Can negative output of DRV2667 be left floating? Powerhap needs to be driven single ended

robin harvey
Prodigy 60 points
Part Number: DRV2667

Hi,

I  am trying to drive the Powerhap actuator from TDK with the DRV2667

Judging from the datasheets for the powerhap it seems that it cannot be driven negatively, however apparently you tested the same actuator so I am interested in whether or not you drove it differentially anyway.

Assuming you can't I have figured there are two ways in which to drive the actuator single ended using the internal Ram which is essential to my project.

Driving only with direct waveforms ranging between 0x00 and 0x80, this is less ideal for me as driving purely with direct waveforms puts limitations on the 2kb ram, and is also rather time-consuming.

Leaving out- floating and only driving using out+ and driving with Synthesized wave-forms as well, judging from FIG 10 on the datasheet it seems that the sinusoids are generated by two combined differential sinusoids on both outputs rather than say two half-bridge rectified waveforms, is this correct or will the shapes of the individual sinusoids be significantly different with an unbalanced load?

So will leaving one output of the DRV2667 floating, aka an very unbalanced load cause any issues/damage to the DRV2667 (the load of the powerhap actuator in question is 1uf)

Regards,

Rob

  • 0
    TI__Intellectual 1910 points
    Hey Rob,

    Sorry for the delay. In order to make the DRV2667 output single ended, you should ground the OUT- terminal. Yes, I drove the Powerhap actuator with only one terminal (OUT+) connected and the other terminal of the actuator grounded. The OUT- is simply the inverse of the OUT+ pin, not a separately generated signal, so an unbalanced load will not cause a problem.
  • 0 in reply to Micah B Brouwer
    Prodigy 60 points
    Hi, thank you for the advice I have tested the powerhap and found, for this driver at least, that two Murata piezo elements soldered back to back all around the edges with a 1mm airgap inbetween the brass plates was far superior in terms of both efficiency, tactile response and cost, might be worth checking out, actually about that I'm trying to find out whether for short waveforms the 30vpp limit of piezo elements can be safely and repetitively exceeded since overheating is no longer a problem. Don't suppose you know anything about this?

    Also the datasheet doesn't mention how to drive single ended, so although obvious it's always nice to have clarity ;)

    Regards,

    Rob
  • 0 in reply to robin harvey
    TI__Intellectual 1910 points

    Hey Robin,

    Thanks for pointing that out, differential vs single-ended output is a fairly common question. As far as piezo performance, I cannot recommend exceeding any limits that are stipulated in the respective datasheets, but I will say that the DRV2667 will be able to output much higher voltages when the load has a smaller capacitance. As noted in the datasheet, the DRV2667:
    - Drives up to 100 nF at 200 VPP and 300 Hz
    – Drives up to 150 nF at 150 VPP and 300 Hz
    – Drives up to 330 nF at 100 VPP and 300 Hz
    – Drives up to 680 nF at 50 VPP and 300 Hz

    As you mentioned earlier, the 7G PowerHap from TDK has a typical capacitance of 0.9uF according to its datasheet, so its max output voltage is limited accordingly. If you like the design of the PowerHap actuator, you might try the smaller 2.5G version and see if it suits your needs.