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[ DRV2604L ] Open Loop Frequency Resolution

Kenichiro
Mastermind 9165 points
Other Parts Discussed in Thread: DRV2604L, DRV2604

[ DRV2604L ] Open Loop Frequency Resolution

Hi expert,

If I calculate the open loop frequency for LRA with equation (2) below,

Open loop frequency is something like this.

OL_LRA_PERIOD[6:0]

0x31: 207.2Hz

0x32: 203Hz


Is there any way to driver my LRA with 205Hz with open loop mode?

I accept that the benefit of ART can not be achieved with open loop mode. However it's necessary to prevent unexpected noise from LRA.

Do I need to use PWM mode (128 times of driving frequency)?

Thank you for your support in advance.

Regards,

Ken

  • 0
    TI__Expert 8940 points
    Hi, Ken:

    I think you need o use the PWM input mode for such application.

    just out of curiosity, why would you think the ART can make unexpected noise from LRA?
    ART can achieve more acceleration with less drive power.
    For certain amount of acceleration, DRV2604L use less drive power than open loop mode. And usually it doesn't cause noise from LRA.

    Thanks.
  • 0 in reply to Peter Li79
    Mastermind 9165 points

    Hi Peter,

    As you may aware, many of LRAs from multiple supplier specify their specification only with 205Hz input frequency. Yes, the ART of DRV2604/L allow system to make acceleration with better efficiency (means leass power, more acceleration), however, by using ART, the resonance frequency is a bit shifted from 205Hz. For some LRAs, 208Hz, others may be 210Hz...and so on. From customer view point, fixed frequency driving is preferred for some cases.

    Of course, I have tried to argue that ART gives the benefit such as better efficiency, less acceleration variation and so on.

    Please let me know, if you have other comments.

    Thanks,

    Ken