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2pcs AD7768 Simultaneous Sampling ODR query

negon.meng
on May 14, 2019

Dears :  

  I intend to use AD7768 at this application : 16channel simultaneous sample  , connecting two parts with daisy chain , per channel sample 102khz signal  . my question is if the output date rate can support it ?

  • FormerMember
    0 FormerMember on May 15, 2019 11:39 AM over 1 year ago

    Hi,

    There are a number of factors to be considered here:

    • There is a formula on page 73 which specifies the maximum DCLK frequency that can be used when daisy chaining. See image below.I would recommend operating the part with IOVDD = 3.3V. Care needs to be taken in order to meet timing so that tp and tskew are kept as close to zero as possible. This is the limiting factor that I can see.
    • In order to achieve 102kSPS ODR you will need to run the MCLK at 26.112MHz. DCLK = MCLK must be used in order to get all the data output from the part and two DOUTs will be needed.  
    • The ODR can be achieved by using Fast power mode, decimate by 64 or Median power mode, decimate by 32.

    If there is any possibility tp and tskew cannot be kept low (3 ns or less) I would recommend using two separate interfaces. You can still operate the parts in pin control mode if you wish.

    Regards

    Niall 

  • +1 on Jan 20, 2021 5:25 PM 1 month ago

    Hi,

    There are a number of factors to be considered here:

    • There is a formula on page 73 which specifies the maximum DCLK frequency that can be used when daisy chaining. See image below.I would recommend operating the part with IOVDD = 3.3V. Care needs to be taken in order to meet timing so that tp and tskew are kept as close to zero as possible. This is the limiting factor that I can see.
    • In order to achieve 102kSPS ODR you will need to run the MCLK at 26.112MHz. DCLK = MCLK must be used in order to get all the data output from the part and two DOUTs will be needed.  
    • The ODR can be achieved by using Fast power mode, decimate by 64 or Median power mode, decimate by 32.

    If there is any possibility tp and tskew cannot be kept low (3 ns or less) I would recommend using two separate interfaces. You can still operate the parts in pin control mode if you wish.

    Regards

    Niall