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ADS1278 maximum trace length

umamaheswar peta
Expert 1370 points

Other Parts Discussed in Thread: ADS1278

Hi,

We are using ADS1278 in one of our design, pls clarify below queries.

  1. While using the ADS1278 chip, what is the maximum trace length that clock signal from the driving source(crystal oscillator) to the ADC should be considered?
  2. If two ADS1278 are used in design which are connected in a daisy chain, then what should be the maximum trace length of common clk going to both the chips from the source to destination?

Rgds,

Uma Mahesh

  • 0
    Expert 1370 points

    Hi,

    Can anyone help to answer below queries.

    What is the maximum trace length should be for the differential pair routed analog inputs given to ADS1278 from transducers?

    Rgds,

    UmaMahesh

  • 0 in reply to umamaheswar peta
    TI__Mastermind 23235 points
    Hello Uma -
    There is no trace length requirements, minimum or maximum, for the ADS1278. For clock lines, generally you want to keep them as short as possible since they are usually higher frequency, but this is more of a general PCB guideline and not a requirement of the ADC.
  • 0
    TI__Guru** 100935 points
    Uma,


    One other reason to keep the trace length short is that the often the crystal is sensitive to capacitive loads. If the crystal is far away, this adds extra load capacitance. Most crystals will require some load capacitance, but it doesn't take much trace to build several pF of capacitance into the line.

    Load capacitance is something the crystal manufacturer specifies, and you can calculate the approximate trace capacitance based on it's dimensions.


    Joseph Wu