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DRV2604L / variation in output waveform

K.Yaita
Guru 29720 points
Other Parts Discussed in Thread: DRV2604L, DRV2604
Hi Team,
 
My customer is evaluating DRV2604L.
He pointed out the waveform changes with each 3 hit(①～③) regardless of the same condition.
I also heard that waveforms of ①～③ could be the same waveform sometimes.
 
The following waveform is the case that ①～③ are all different.
Especially current waveform(CH2) are definitely different.
 
-CH1:output voltage
-CH2:output current
 
 
Even if 1 hit pattern(only ①), it seems the waveform changes by each hit.
 
Is it possible case of DRV2604L? Could you please give me your comment?
If you need additional information, please send me email. 
 
Your support would be appreciated.
 
Best Regards,
Yaita / Japan disty
  • 0
    Guru 29720 points
    I heard this variability doesn't be occured only DRV2604L but also DRV2604.
    Is this variability of waveform possible case of DRV2604/DRV2604L?
     
    Best regards,
    Yaita
  • 0 in reply to K.Yaita
    TI__Genius 12485 points

    Yaita-san,

    The variability could be arising because the LRA is probably still moving and has not come to a complete stop. The solution to this is to increase the magnitude of braking or adding a wait till the LRA stops completely. Could you please take a capture of the acceleration waveform? (Also, what is the waveform on CH1? it does not look like Output Waveform)

    Regards,

    Gautham

  • 0 in reply to Gautham
    Guru 29720 points
    Hi Gautham-san,
     
    I apologize for mistaking.
    CH1 is acceleration waveform that is captured by vibration meter VM-83(RION).
    He put smartphone on cushioning material and picked up from the surface of LCD.
    *using double-stick tape to fix the pick up and LCD(smart phone)
     
    My customer said he could observe the waveform variability even if LRA complete stop.
    He thinks the variability is no ploblem for his application,  however he would like to know if it derives from the device(DRV2604L).
     
    Best regards,
    Yaita
  • 0 in reply to K.Yaita
    TI__Genius 12485 points

    Yaita-san,

    Attached below is an example Triple_Click from the library waveforms. The waveform provided by you has all overdrive cycles only. (no overdrive to rated transition).

    You can tune the Back-emf gain parameter(0x1A) to get more consistency and repeat on multiple LRAs. (atleast 3 units)

    Please let us know if you need more information. 

    Regards,

    Gautham

  • 0 in reply to Gautham
    Guru 29720 points
    Gautham-san,
     
    Thank you for your reply.
    I will inform this to my customer.
    I appreciate for your support.
     
    Best Regards,
    Yaita
  • 0 in reply to K.Yaita
    Guru 29720 points

    Hi Gautham-san,

    My customer tried to increase the value of BEMF_GAIN[1:0] and confirmed it is efficient for consistency.
    However he felt brake is weaker than before.

    Then, how do I adjust the srength of brake?
    Do I achieve it to increase overdrive voltage?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 12485 points

    Yaita-san,

    Yes there is a way :)

    Could you recommend to try increasing the Brake Factor using the Feedback Control Register?

    Regards,

    Gautham Ramachandran

    Apps. Engineer- Haptics.

  • 0 in reply to Gautham
    Guru 29720 points

    Gautham-san,

    Thank you for your prompt reply!
    I will inform it to my customer.

    Best Regards,
    Yaita