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DRV2700EVM-HV500: kHz switching capabilities & input filter

Alessia Scriminich
Prodigy 20 points
Part Number: DRV2700EVM-HV500
Other Parts Discussed in Thread: DRV2700

Hi,

I'd like to use the DRV2700EVM-HV500 to switch a 14pF load between 0V and 400V, ideally at a frequency above 10kHz.

The DRV2700 datasheet reports a low-gain bandwidth of 20kHz, however, I understand the low-pass filter in the EVM limits the maximum frequency.

What's the maximum frequency I can switch this load at with the EVM?

Is it possible to modify the parameters of the filter to move the 3dB point upwards, or even bypass it?

Thanks.

  • 0
    TI__Intellectual 1910 points

    Hey Alessia,

    Piezo Control Console is the software used to control the DRV2700EVM-HV500 and it gives you the ability to adjust the PWM input frequency from 10 Hz to 50kHz. However, the input filter on the EVM will attenuate signals between 1 kHz and 20 kHz to somewhat resemble a PWM signal while signals greater than 20 kHz will basically be DC.

    The input filter is discussed in depth in section 7 of the datasheet. The RC network on the EVM has a 3-dB point around 1.75 kHz. If the signal at 10 kHz is attenuated too much for your application, you can modify the input filter (by manually replacing the resistors and caps) but we do not recommend setting the 3-dB point beyond 5 kHz.

  • 0 in reply to Micah B Brouwer
    Prodigy 20 points

    Hi Micah,

    Thank you for your reply.

    The output signal I need for my application should reproduce a square wave if possible, so I'm thinking of modifying the filter to get a better response.

    Is there a specific reason for not moving the 3-dB point above 5kHz? How about the bypass?

    Regards,

    Alessia

  • 0 in reply to Alessia Scriminich
    TI__Intellectual 1910 points

    Hey Alessia, 

    As the output voltage increases, the bandwidth of the amplifier is limited due to the nature of the device. The device may not be able to achieve 400 V at such high frequencies. 

    Please note that in addition to a low-pass RC filter at the input, there is also an op-amp integrator used to both smooth the input signal and to control the output voltage. The output controls the virtual ground of the feedback network, and so it should not be modified without considering the rest of the system. 

    You could try and stretch the limitations of the device for your use case, but it may be difficult to achieve a 400 V output at 10 kHz. Please let us know if modifying the input filter satisfies your requirements.