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ADS131A02: Noise and internal reference query

Rohit J
Intellectual 850 points
Part Number: ADS131A02
Other Parts Discussed in Thread: LM7705

Hello,


I had a couple of general questions regarding ADS131A0x -

1. Is there any quantifiable noise performance impact by using the internal negative charge pump vs an external charge pump like LM7705? I would prefer to get rid of the external circuit to save cost but would like to know what kind of noise impact I should expect to see using the internal supply.

2. I am using the internal voltage reference. Would it be possible to buffer the output at REFP and feed it as a reference to a different circuit (assuming I do not violate the 100uA spec)? How would this impact ADS131A0x's performance?

Thanks,

Rohit Joshi

  • 0
    TI__Intellectual 2885 points
    Hello Rohit,

    1. The biggest difference between an internal and external charge pump is the switching frequency at which they work. The benefit of using the internal charge pump is that it uses the same clock at the ADC. The switching frequency of the internal charge pump will be 2f_MOD, which will fold back to 0 ideally. If you use an external charge pump be sure to select a c_FLY that will be in the stopband of the f_data you select.

    2. If you provide a buffer the REFP, you should be able to use it with no problems. What are you planning to use the REFP for?
  • 0 in reply to Matt Mendez
    TI__Intellectual 850 points
    Hello Matt,

    1. Thanks for the comparison. I have decided to proceed with using the internal charge pump. I am assuming that there is negligible impact to noise contributed by doing so. Can you please confirm?

    2. I was going to use it as a reference point in a comparator. I don't need to do that anymore so won't be touching that pin.

    Thanks,
    Rohit