• Resolved

DRV2605: Cannot get haptic feedback either with LRA or Piezo

Part Number: DRV2605

Hello,

I am trying to get a haptic feedback either using LRA motor with DRV2605, or using piezo with DRV2605/DRV2700 (based on application report SLOA255).

When using just LRA, the haptic feedback is barely noticeable. However, when the LRA is driven directly from a power supply, the feedback is strong.
When using the DRV2700 with a signal from DRV2605, there is no feedback can be felt. I also notice that the FB pin does not output 1.3V. Thus my PVDD signal is around 10V instead of 65V.

Attached is the schematics of the haptic driver circuit. The selection between Piezo or LRA is done using J1 and J2 jumpers.

LRA motor - 1020-15-003-001 (www.digikey.ca/.../j2rmtd)
Piezo - Z63000Z2910Z 1Z 2 (www.digikey.ca/.../j2rm8v)

I am looking for any possible recommendation.

Thank you.

Regards,
Leon

  • Hi Leonid,

    Welcome to E2E, thanks for your interest in our devices.
    My colleague is out of the office, so He will be responding tomorrow with further information.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • Hi Leon,

    I'll give a close review to the schematic but I have a couple comments at this moment:
    - Low-Pass Filter is not populated on the schematic (R37, R39, C8 and C9). Have you tried to place these components to form the LPF? The output signal from DRV2605 is a Class-D, so the filter is needed for the analog inputs of DRV2700.
    - You mention LRA motor for the DRV2605 actuators, but from the device description in its data sheet and digikey, as well as your comment about driving it with DC voltage, it looks more like a motor (like ERM). Are you configuring DRV2605 to drive an LRA or ERM actuator? If you're trying with LRA config, I would suggest to change it to ERM.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low power Audio & Actuators
  • In reply to Ivan Salazar:

    Hello Ivan,

    Thank you for your prompt reply.

    For some reason, I thought that the motor is LRA type. I will update the registers and will test it as ERM motor.

    Regarding DRV2700 I have a few questions:

    1. I can definitely populate the LPF. What would be recommended cutoff frequency?
    2. While LPF might help to propagate the signal properly, I still have very low voltage on FB (around 0.3V). Thus, my PVDD is around 10V. I assume LPF does not control the internal boost converter. Why voltage on FB pin so low?

    Regards,

    Leon

  • In reply to Leonid Hrapunsky62:

    Leon,

    Please let us know the results after changing device config for ERM.

    Regarding the schematic I found the following:
    Rext is 4-kohm? The minimum recommended from the data sheet spec is 6-kohm, the current limit for the boost might be out of spec. In addition, the current limit of the boost should be less than the rated saturation of the inductor L2. Using 4-kohm as Rext would set a current limit of around 3.5-A (theoretically as this is out of spec).

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low power Audio & Actuators
  • In reply to Ivan Salazar:

    Hello Ivan,

    I wanted to update you regarding the motor test. After changing the registers to drive the ERM motor, the performance of the motor immediately improved. We will continue playing with registers to get the best results.

    I understand your point regarding REXT on the DRV2700 circuit. I will replace the resistor and will update you on the results.

    Thank you again for continuing support.

    Regards
    Leon

  • In reply to Leonid Hrapunsky62:

    Hi Leon,

    Please let us know the results of changing Rext; hopefully this will solve the situation with DRV2700.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • In reply to Ivan Salazar:

    Hello Ivan,

    Sorry for the delay in responding.

    As mentioned in the above post DRV2605 works properly for us.

    However, the DRV2700 still does not perform. I replaced REXT resistor to 10k. Unfortunately, it did not improve the performance. As soon as the EN pin is asserted high, the supply voltage drops from 5V to around 3.5V - 4V (board-dependent). Any suggestions? Troubleshooting steps?

    Thank you.

    Regards,
    Leon

  • In reply to Leonid Hrapunsky62:

    Hi Leon,

    Thanks for the update. Is there a chance that you could share the voltage rating of the capacitors from your schematic? I'd like to make sure that the caps are rated for the correct voltage, I'm specially interested on the ones related to the boost.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • In reply to Ivan Salazar:

    Hi Ivan,

    All capacitors that are used for DRV2700 are 100nF, X7R, 20%, 50V (CGA2B3X7R1H104M050BD). I realize that C13 is below expected 68V boost voltage, but speaking with cap manufacturers, at 23 deg C, the capacitors can take significantly higher voltage than rated.

    Anyway, if you believe that this might be an issue, please let me know and I will try to find a capacitor with a higher voltage rating.

    Regards,
    Leon

  • In reply to Leonid Hrapunsky62:

    Leon,

    For troubleshooting you could try a couple things:
    - Higher voltage rated cap on PVDD/BST
    - Disconnect DRV2700 input from previous stage (DRV2605)
    - Power DRV2700 with its own supply, eg. power up only DRV2700 and do not supply other devices in the system with the same source
    - In case of powering DRV2700 with batteries, change for DC Voltage Supply to check if current could be an issue

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators