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High Dynamic Range using two ADCs?

Art Wagner
Prodigy 160 points
Other Parts Discussed in Thread: ADS1262

Is it possible to achieve a dynamic range of 160 dB using two ADCs? One ADC channel would have a gain of 1, while the other ADC channel would have a much higher gain.

  • 0
    TI__Intellectual 1130 points

    Hi Art

    If a high precision SAR ADC architecture is used, the gain for the other channel needs to be somewhere 60dB (1000) or 80dB (10000). It may be little easier to synchronize the two ADC channels with the SAR architecture.

    A Delta-Sigma ADC architecture will provide a much higher dynamic range so it will reduce the front end gain requirements. What is your sampling rate requirements for this system.

    Thanks

  • 0
    TI__Guru* 97805 points
    Art,


    I don't know of any realistic way of achieving higher resolution by combining two data converters. That's like having 40nV of resolution on a +/-2V scale. While it may be possible to have that size of an LSB (if you have a smaller full scale and are using some sort of PGA), I don't see how you can do it with larger scales.

    On top of the difficulty of being able to align LSBs of one ADC to the full scale of a second ADC, you'd also need a reference that has a similar noise floor.

    Regardless, with precision ADCs of the delta-sigma variety, you can get rather good resolution. For the ADS1262, depending on mode, you can get 25.0 bits as an Effective Number of Bits noise free. This becomes 1/2^25 of the full-scale. For resolution, 1/2^25 is about 150dB of resolution. Just remember that the noise of the reference is a contributor to noise in the measurement.


    Joseph Wu