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  • TI Thinks Resolved

DRV2625: DRV2625 VDD versus LRA waveform Vpp

Intellectual 940 points

Replies: 31

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Part Number: DRV2625

Hi

We set overdrive voltage = 3Vpeak as attached excel

But we find when we change DRV2625 VDD voltage, the waveform Vp/Vpp also change as below table

Is it normal? Since as I know the Vp should limit at Vpeak setting

Thank you~~

Haptic_VDD(V) Waveform Vp(V) Waveform Vpp(V)
4.4 3.42 6.84
4.2 3.34 6.68
4 3.3 6.6
3.8 3.22 6.48
3.6 3.14 6.32
3.5 3.1 6.2
3.4 3.06 6.12

8132.DRV2624 and DRV2625 Configuration Tool and Design Equations-AWA_modified.xlsx

  • Hi, Poki,

    Are you modifying the VDD level after the DRV2625 has been configured? I mean, could you verify if you get different results under the tests below?

    - Set the VDD level, then configure the device. Measure the Vp and Vpp level. Power down the device and change the VDD level to see the difference.

    - Set the VDD level, then configure the device. Measure the Vp and Vpp level. Modify the VDD level without power down the device to see the difference.

    Please let me know if you have questions or comments on this.

    Best regards,
    Luis Fernando Rodríguez S.

  • Hey Poki,

    It should not be going past 3V if that what the clamp voltage is set at, I will run some tests on my own to see if I come up with a similar pattern. From the other threads we have been discussing I know you have multiple chips, are they all showing these results? Is the rated voltage acting as it should?

    Also are these values with an LRA attached?

    Best,

    Carson

  • In reply to Luis Fernando Rodriguez S.:

    Hi Luis:

    I do both test and get the same result as above table

    Have you check attached .xlsx file? Any problem about it?

    Thank you~~

    Poki

  • In reply to Carson Allen:

    Hi Carson:

    Yes I test another chip and get the same result, Vp/Vpp level change with VDD level with above two setup, those test attached LRA

    (- Set the VDD level, then configure the device. Measure the Vp and Vpp level. Power down the device and change the VDD level to see the difference.

    - Set the VDD level, then configure the device. Measure the Vp and Vpp level. Modify the VDD level without power down the device to see the difference.)

    And the rated voltage(Vrms) should increase with VDD increase since the waveform shape not change, only change Vp/Vpp, I attached some as below

    Waveform is strong click 100%

    VDD=3.4V

    VDD=4V

    VDD=4.4V

    Poki

  • In reply to Poki Huang:

    Hey Poki

    I think your problem might be due to the fact that you are too zoomed into you oscilloscope and are picking up a lot of the PWM noise which is the all fuzziness at the peaks of the wave forms. If you zoomed out and then took measurement of the peaks it may give more consistent result that at your OC_CLAMP voltage.

    So measured with a large time division and show and examine those results

    Also are you making sure to either auto-calibrate or reload in the calibration value settings from the host processor every time you turn on and off when you change VDD.

    Best,

    Carson

  • In reply to Carson Allen:

    Hi Carson:

    Yes when we change VDD, we turn off system, setting VDD, and turn on system.

    We check PWM signal (before low pass filter) with VDD=3.6V and 4.4V, we found the Vp will increase with VDD and the Vp is almost equal to Vp as below chart

    Is it normal or not? If not, seems our OC_CLAMP=3V didn't work, have you check attached .xlsx file and if any wrong?

    VDD=3.6V, measured Vp=3.54V (by cursor)

    VDD=4.4V, measured Vp=4.38V (by cursor)

    Also we check waveform top detail (after low pass filter) and find there is PWM signal inside

    We use your DRV2605 EVB low pass filter (100Kohm and 470PF)

    Is it normal?, If yes, the ripple high and low gap is ~480mV, which one should we use to calculate Vrms?

       

  • In reply to Poki Huang:

    Hi Carson:

    Could you help do same test that setting RATED_VOLTAGE=1.8V, OC_CLAMP=3V, and change VDD=3.6V and 4.4V to see waveform Vp level?

    Thank you~~

    Poki 

  • In reply to Poki Huang:

    Hi Carson:

    Sorry add one question

    You said there's PWM noise on top of waveform

    So you mean we take below chart red arrow area as Vp?

  • In reply to Poki Huang:

    What I am saying is when you have it zoomed in like you do you see ripple from PWM which will make the waveform look like it is going above my clamp voltage of 3V.

    Where as if you zoom out on this same waveform that switching frequency is not picked up and see that the waveform is not going past 3V like this:

  • In reply to Carson Allen:

    So when trying to calculate Vrms and Vpeak try to freeze it at a large time scale and zoom in so the PWM is not being picked up and it looks like this:

    Try doing that and see if you get it to obey your clamp voltage setting even when you vary the VDD.

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