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ADS127L11: Reference capacitor CREF

FZ
Prodigy 30 points
Part Number: ADS127L11
Other Parts Discussed in Thread: OPA328

Tool/software:

Hello,

how large is the reference capacitor CREF on the ADS127L11?

I need the value to simulate if my external reference voltage buffer settles fast enough.

  • +1
    TI__Mastermind 40870 points

    Hello FZ,


    The equivalent reference input capacitance for ADS127L11 is 10pF.  Note that is you use the REFP buffer, the equivalent input capacitance is reduced by more than 100x.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 30 points

    Hello Keith Nicholas,

    thank you very much.
    The internal REFP buffers must be deactivated because I want to operate the ADC with AVDD1=3.3V (low-speed mode) and use a 3.0V reference.

    I am planning to use the OPA328 (as shown in sboa558) to buffer the REF35300 voltage reference.
    On my simulations, the reference voltage settles fast enough (using fmod=1.6385MHz).

    Do you think this buffering circuit is suitable for this application?

  • +1 in reply to FZ
    TI__Mastermind 40870 points

    Hello FZ,

    Yes, the OPA328 will have more than enough bandwidth to drive the ADS127L11 REFP input.

    Regards,
    Keith