How to read the Input range of ADC?

Discussion in 'Homework Help' started by patheticz, Nov 3, 2009.

  1. patheticz

    Thread Starter New Member

    Nov 3, 2009
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    I have been reading through ADC data sheet, but is having difficulty in getting the range of the analog input of ADC.
    I understand that the ADC works based on setting the Vref, and connecting the required analog input to the ADC to digitize it.
    However, i also understand that there will be a limit to how high the Vref can be for each ADC.
    Which is the field that i am supposed to take note in order to identify the maximum range of input the ADC can take.
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    Data sheets are sometimes hard to read. Post your data sheet. And we will help
     
  3. patheticz

    Thread Starter New Member

    Nov 3, 2009
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    Theses are two of the data sheets i came across.
    Thanks.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Those are really gonzo ADC's. I would not suggest you try to use either as a starting exercise. 16 bit ADC's are hard to make use of.

    On page 16 of the THS1206 ADC is the paragraph that tells how the reference voltage works.

    You might find this section of our Ebook interesting - http://www.allaboutcircuits.com/vol_4/chpt_13/10.html
     
  5. t06afre

    AAC Fanatic!

    May 11, 2009
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    This should help I hope.
     
  6. davebee

    Well-Known Member

    Oct 22, 2008
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    The THS1206 data sheet says that the full-scale reading is the value on pin VREFP,
    and the zero-scale reading is the value on pin VREFM. Internally, VREFP is set to 3.5V and VREFM is set to 1.5V, but you can modify those values by applying your own voltages to the pins REFP and REFM.

    The ADS8254 needs an external reference voltage in the range of 3 to 4.2 volts,
    and accepts input signals in the range +/ vref.

    So in both cases, the voltage on the high reference pin is the max the chips are supposed to accept.

    I'm not sure what gonzo means but the ADS8254 is a fairly complicated ADC - it needs three different supply voltages. But the THS1206 doesn't look too difficult to work with.
     
  7. patheticz

    Thread Starter New Member

    Nov 3, 2009
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    So does that mean that THS1206 can only take in value that is from 1.4V to 5.25V -1.2V = 4.05V?

    Are there any recommended ADC that is capable of sampling at 1MSPS or higher, and is able to provide a range of ±5 or ±10V?
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    You can go to manufacturer's sites (Analog Devices, National Semiconductor, Texas Instrument for some) and do a parametric search.

    You might also wish to think of the interface, number of selectable channels, and resolution.
     
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