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Original question:

DRV2700EVM-HV500 : I have noise

DRV2700EVM-HV500: Reducing >1 kHz noise on piezo driver output (HD-PAF1419)

Muneeb Ahmad
Prodigy 40 points

Part Number: DRV2700EVM-HV500
Other Parts Discussed in Thread: DRV2700EVM, DRV2700

Tool/software:

I’m driving a HD-PAF1419 piezo actuator from an ESP32. The ESP32 reads an audio signal and, when a threshold is exceeded, outputs a PWM signal to TP1 to enable the amplifier.

When the PWM input is zero (disabled), I still observe noise on the amplifier output (OUT+ / OUT−) around 3–8 kHz, which produces an audible/physical buzz in the piezo. I want to attenuate frequencies above 1 kHz (the actuator operates up to ~500 Hz).

What is the best way to reduce this high-frequency noise on the amplifier output?

  • 0
    Prodigy 40 points

    I have tried to enable the device by applying the external control signal to EN (middle header of JP3). But the device is not producing any voltage.

  • 0 in reply to Muneeb Ahmad
    TI__Expert 5480 points

    Hi Muneeb,

    By default, the DRV2700EVM uses the MSP430 PWM input mode with a low-pass
    filter. In this mode, the onboard MSP430 generates a PWM
    waveform that is sent through the low-pass input filter to the DRV2700. Do you see the noise at the default mode?

    You can check section 5 of the EVM user guide. https://www.ti.com/tool/DRV2700EVM-HV500

  • 0 in reply to Hailong Chen
    Prodigy 40 points

    Thank you Heilong for your reply.
    I am using an external PWM signal from ESp32 to actuate the piezo actuator, and followed section 5.2 (Analog input).
    By running the noise at the default mode, there is no noise.

    I have added two resistors at the output of the DRV2700EVM. Each resistor is connected to each output terminal. As given below.

    OUT+ — R(5KOhm) — piezo(+)
    OUT− — R(5KOhm) — piezo(−)

    After that, I have heard no buzz sound on the Piezo actuator. I forgot to see the output on the Oscilloscope. I will run it again and share the output.
    Is there any better way then kindly let me know.
    Thanks for your help.

  • 0 in reply to Muneeb Ahmad
    TI__Expert 5480 points

    If the default mode has no noise, it means the DRV device works normally. It seems the 5kOhm attenuates the noise, which can be a tentative workaround. You can test the few test points along the signal chain and see where the noise comes from.