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DRV8662EVM: Driving high capacitive load

Kit Yeung
Prodigy 40 points
Part Number: DRV8662EVM
Other Parts Discussed in Thread: LM48580

Hi,

I am evaluating DRV8662EVM with TDK's PowerHap 2626H023V120 (datasheet: www.tdk-electronics.tdk.com/.../2626H023V120.pdf) and currently facing some questions for using the EVM.

1. According to the manual, the EVM is capable of bipolar output, while the piezo element uses a unipolar input if large displacement is desired. Is it ok to connect only the OUT+ to the actuator's positive terminal, and connect OUT- to ground with a small cap?

2. It seems that the actuator's capacitance is high (4.4 uF) compared to the EVM's recommended actuator (nF level). Is there any modification/alternative EVM to drive this type of actuator?

Best,

Kit

  • +1
    TI__Mastermind 20775 points

    Hi Kit,

    You can connect only one output to the Piezo element, however you should keep in mind that the output is biased at ~PVDD/2 with no input.

    Yes, 4.4uF is a bit high for this device. This will limit the bandwidth that the amplifier can drive. the bandwidth limit is mostly determined by the output current capability of the boost converter.  If you want to maximize the current capability of the boost you can do a few things

    -set Rext to the minimum value - 6kOhm

    -use a larger boost inductor, >1A Isat, and >5uH

    We have another family of piezo drivers, LM48580, but these devices can only drive up to ~15V single ended, Which may not be enough in your case.

    Regards,

    Arthur

  • 0 in reply to Arthur Brown
    Prodigy 40 points

    Hi Authur,

    Thank you for your reply, I will modify the driver and see how the actuator performs.

    Best,

    Kit