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Original question:

ADS122C04EVM: Delta-Sigma ADC Evaluation Software Does Not Connect to EVM

ADS122C04EVM: Data converters forum

Pratik Sharma
Intellectual 380 points
Part Number: ADS122C04EVM
Other Parts Discussed in Thread: ADS122C04, ADS8900B

hi.

I have a application specific theorital doubt, i want to sample 50Hz AC wave form at a sampling rate of 25.6 Khz (@24bits), But in data sheet i see (datasheet table) where it specifies data output rate effected by OSR (oversampling ratio) and I assume for my application i have to set a OSR of 160 to get data out of it at a rate of 25.6 Khz (my assumtion may be wrong). And also it states it will reduce effective no of bits to somthing like 16.
why it is not it is simple like In other ADCs (SAR) where we have to just make (SPI-CS ) line low to sample.

Is this right ADC for my application...?

  • 0
    TI__Guru**** 180941 points

    Hi Pratik,

    You won't be able to achieve 25.6 KSPS with the ADS122C04.  This device is limited to 2KSPS MAX and the OSR is fixed by the chosen gain, sampling rate and operating mode (Turbo vs. Normal).  The ADS122Co2 is a delta-sigma converter, meaning it oversamples and provides you with a time averaged result.  SAR converters take a single sample and convert that to provide a 'snap shot' of the input at a particular sample instance.  Unfortunately, there is no way to make the ADS122C04 behave like a simple SAR converter.

    If you can provide a little detail on your application and your need to sample at 25.6KSPS, we might be able to find an alternate solution for you.

  • 0 in reply to Tom Hendrick
    Intellectual 380 points

    Hello Tom, 

    I am pursuing PhD (Power Engineering)..working on some power analyzer for my smart grid project... I need to sample a 50Hz ac signal with high resolution (24 bit) and at a high sample rate (25.6 Khz), so i am looking for ADC which have atleast 2 channel, must simultaniously sample its channels and SPI communication for data tranfer will be preferred.. (I am using intel cyclone V FPGA to read those.) 

    and adc should simultaniously sample both channel strictly when sampling pulse input is provided (like making CS-pin LOW or anything similar).. "i am not concerned about the price" please suggest my some ADC for my application .. 

  • 0 in reply to Pratik Sharma
    TI__Guru**** 180941 points

    Hi Pratik,

    At the moment, we have the ADS8900B series of SAR ADC's which offer 20bit resolution.  These are single channel devices, but you could use 2 in a series (daisy chain) or parallel (star) configuration.  Assuming the convert start (CONV) of both devices came from the same host source, you would have simultaneous sampling capability.  We do have true simultaneous sampling devices (multi channel in a single package) but you would be looking at 16-bit resolution in that case.

  • 0 in reply to Tom Hendrick
    Intellectual 380 points

    Tom,
    I will be looking for ADS8900B series of ADCs..  it supports 1000 K samples per second.. ! I will use two of them in parallel... and i assume it does not need to additional configuration and settings like in delta sigma type adc .... and i may like to provide my 50Hz AC input as Pseudo differential to the ADC...