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Using DRV8662 amplifier only

Other Parts Discussed in Thread: DRV8662

Hi,

Is it possible to bypass (not use) 8662 boost converter by suppling external 100V to PVDD pin? How gain can be set in this scenario? 

Kind regards,

Alex

  • Hello Alex,

    Thank you for looking at the DRV8662! The amplifer is driven off of the boost voltage so using the higher voltage will still work with the amplifer section.  However, other parts of the circuit will need to be driven off of Vdd.

    - Will you be able to still provide 5V to Vdd?

    - What is the reason to not use the boost converter?

  • Thanks Rodney,

    Yes, I can provide 5V to Vdd. And just leave SW, Vbst, Vpump, FB and REXT floating - right?

    Reason for considering this approach is that boost converter runs at fairly low frequency and noise in the outputs generates an audible "hiss" with the type of actuators I am using. Filtering and tinkering with L,C values helps but problem still persists.

    Regards,

    Alex

  • Alex,

    I'm not sure that you can float those because they are part of a feedback loop for the boost converter and will be in an unknown state. Let me look into this a little bit to see what we can do to help with the "hissing".

  • Rodney-

    Thanks for your help. I do not really care about the state of converter assuming there is no impact on the rest of the chip but having better knowledge about 8662 internals would help certainly.

    As for the switching noise - it is our 3rd design using 8662 with the same result - hence  looking at external PS options.

    Regards,

    Alex

  • Hello Alex,

    Sorry that you are on your 3rd design and I wish we could have helped sooner. I have a solution to disable the boost, however we might be able to tune your current design so that you can still use the boost and now hear the "hiss".

    If you want me to help with your current design, then just let me know on the forum and I will send you an email outside the forum.

    If you want to just disable the boost then you can:

    1. Apply the 5V to Vdd
    2. Apply the 100V to PVDD (be sure to disconnect VBST from PVDD)
    3. Float or tie the SW pin to GND
    4. Tie a large resistor on the Rext pin (30k for example)
    5. Tie Vfb to Vdd
    6. The VPump will still need a small cap (nF) to assure no faults will occur

    I hope this helps and let me know if you have any other questions.

  • Excellent. Thanks Rodney

    /Alex