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ADC selection

harish jangid
Prodigy 70 points
Other Parts Discussed in Thread: INA129, PCM1808, ADS7813, ADS1248, ADS1248EVM-PDK

Hi,

I build a 8 channel data acquisition system using  " ADS7813P  16BIT ADC, SERIAL O/P, 7813, PDIP16"  ADC. 

ADS7813P  is so expansive so I plane to change the " ADS7813P  16BIT ADC, SERIAL O/P, 7813, PDIP16"  to "PCM1808PWR  ADC, 24BIT, 96KSPS, 5.5V, 14TSSOP".

"ADS7813P"  Price is Rs 3333 and "PCM1808PWR" price  is Rs 195 only.

In my application no need to high sampling rate, Please help me to identify a low cost ADC with good Resolution.

why that much price difference?

  • 0
    TI__Guru* 92655 points
    Harish,


    There are quite a few things to consider when selecting a data converter. What exactly are you measuring? It might help to know about what about the system you want to make to see if we've done something similar.

    Data rate
    Desired resolution and what amount of noise can you tolerate?
    Do you need gain?
    Number of input channels
    Type of interface (I2C? SPI?)
    Are you limited in the amount of power needed?

    If you go into the ti.com website, you should be able to do a quick search on data converters and look through many options.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 70 points

    Thanks Joseph Wu,

    My System Details is 

    Data rate      ---------           i am reading temperature  using thermonuclear and RTD so no need to high data rate.
    Desired resolution and what amount of noise can you tolerate?           ----------               i need high resolution 
    Do you need gain               --------                   No i already used INA129 for gain  
    Number of input channels      ------                 8 channel
    Type of interface (I2C? SPI?)         ------               no issue i can used both type of interface 
    Are you limited in the amount of power needed?          -------             no limited

    Please tell me can i used "PCM1808PWR  ADC, 24BIT, 96KSPS, 5.5V, 14TSSOP" instead of  "ADS7813P  16BIT ADC, SERIAL O/P, 7813, PDIP16".

    also guide me how to select the ADC

  • 0 in reply to harish jangid
    TI__Guru* 92655 points
    Harish,


    I assume that you mean "thermocouple" and not "thermonuclear".

    I wouldn't use the PCM1808 for this application. It's generally an audio adc and used for more ac applications. For the ADS7813, you could use it and it would probably work, but you'd likely have to add some extra circuitry.

    Since you're interested in measuring temperature, I'm going to suggest the ADS1248. It's a bit short on the channel count, with 8 inputs for four differential inputs, but it is designed for temperature measurement with different features to measure RTDs and thermocouples. In particular, there are excitation current sources that you can use for ratiometric measurements with RTDs and multiple inputs for references. It also includes an internal precision reference that you can use for thermocouples.

    Additionally, there's more documentation for how to use the device from a system level. Even if you decide not to use this device, the documentation still can be used to help you put this together.

    Look up the ADS1248 page on ti.com and check the Technical documents section. You can find some application notes on how to use the part:

    www.ti.com/.../sbaa201.pdf

    www.ti.com/.../sbaa180.pdf

    www.ti.com/.../sbaa211.pdf

    Additionally, I'd look at the user guide for the ADS1248EVM-PDK:

    www.ti.com/.../sbau142b.pdf

    Finally, there are a few reference designs for the ADS1248:

    www.ti.com/.../TIDA-00110

    http://www.ti.com/tool/TIPD164

    http://www.ti.com/tool/TIPD120

    Start with the application notes to see how the device is configured for RTDs and thermocouples.


    Joseph Wu