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THS4520: Configuration for 0dB Gain

Sadanori Kato
Guru 36540 points
Part Number: THS4520
Other Parts Discussed in Thread: ADS127L01, THS4551, THS4541

Hi,

I am concerned about whether THS4520 will work stably since it is different with the schematic which is mentioned in THS4520 data sheet.
So, could you please tell me the recommended value for each resistor and capacitor if setting the 0dB gain with THS4520 such as the following schematic ?
* THS4520 is used as the ADC driver for ADS127L01.

Best regards,
Kato

  • 0
    TI__Genius 15975 points
    Hi Kato,

    The THS4520 has ~620MHz of 3dB BW at 0-dB gain, which seems to be an overkill for driving the ADS127L01. Is there a reason the THS4551 is not being considered for the application instead of the THS4520?

    Unlike the THS4520, the THS4551 is a high precision part which is ideal for driving the ADS127L01. You can find schematic of THS4551 driving the ADC in Figure 122 of the ADS127L01 datasheet.

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Guru 36540 points

    Hi Rohit-san,

    Thank you for your reply.

    That reason which will be replaced THS4551 with THS4520 is to improve the THD performance.
    In addition, the THD performance is improved if replacing THS4551 with THS4541, but the 1/f low frequency noise increases slightly, so our customer is considering to use THS4520.
    Could you please tell me your recommended schematic if using THS4520 with 0dB gain ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Genius 15975 points
    Hi Kato-san,

    Replacing the THS4551 with THS4520 for the existing schematic as shown in Figure 122 of the ADS127L01 datasheet should work without any issues. The THS4520 being a voltage feedback amplifier should have minimal dependency to the feedback resistor (RF) of 1.2k.

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Guru 36540 points

    Hi Rohit-san,

    Thank you for the information.

    By the way, could you please tell me whether THS4520 would also work without any issue at the following schematic ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Genius 15975 points
    Hi Kato-san,

    Yes. I think you should be able to use the attached THS4520 schematic while driving the 0.022 uF capacitor. Only thing is that you will not be able to get the filter attenuation at high frequency, which you would otherwise get with the Figure 122 of the ADS127L01 datasheet.

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Guru 36540 points

    Hi Rohit-san,

    Thank you for confirming.

    I expect that THD performance will be improved by high frequency response by using THS4520 and will contact you if I get additional questions from our customer.

    Best regards,
    Kato