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ADS5295: PRBS Function

Richard Elmquist
Mastermind 45250 points
Part Number: ADS5295

Can you go into more detail regarding the PRBS function? The register seems to use 24-bits and the part is just 12-bits. How does this map to the outputs when the customer uses it? Does it map to how he sets up the interface? Is it exactly the same as how you set up the interface to operate? Can you please explain this is greater detail as I have a customer asking the following questions:

I am assuming the PRBS contains the pattern for serial to parallel alignment when programmed to do so. Is this correct? I noticed that this is a 23 bit pattern with a ‘0’ forced at bit 16, (1st bit after the 1st word of PRBS).

Does this repeat in a back to back fashion (the next clock edge after the last bit in the PRBS will be the 1st bit of the next PRBS stream)? Is the correct?

Am I understanding the PRBS function properly based on questions above?

Do we have a document that would explain this in even more detail?

Is there any detailed programming document for the ADS5295?

Thanks for your help with this!

Richard Elmquist

  • 0
    TI__Expert 4145 points

    Hi Richard,

    We have received your inquiry. We will get back to you next week.

    Sincerely,

    Olu

  • 0 in reply to Olu Sodipe
    TI__Mastermind 45250 points

    Olu,

    Any updates on this issue?

    Can you give me an idea when you might be able to offer a response?

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Expert 4145 points

    Hi Richard,

    Thanks for your patience. As you noted earlier, the datasheet doesn't really provide much information on this but I suspect that only the MSB of the PRBS is sent per generated random sequence in place of a single ADC sample. I'm in the process of getting you more definitive information from the IC's designers as it's difficult to tell what bits are selected from the device's output stream.

    Unfortunately, that might take a couple of weeks due to some availability issues. We apologize for the delay.

    What exactly is the customer using the PRBS feature for within their system? There might be other possible solutions we can recommend to that system problem.

    Sincerely,

    Olu

  • 0 in reply to Olu Sodipe
    TI__Expert 4145 points
    Hi Richard,

    We worked through those availability issues more quickly than I anticipated so here is the takeaway from my conversation with my IC designers.

    One 16b PRBS pattern is generated internally per ADC sample by the device. As I stated earlier, the needed number of bits are selected from the MSb side of the 16b pattern and the LSbs discarded based on the serialization factor selected.

    Sincerely,
    Olu
  • 0 in reply to Olu Sodipe
    TI__Mastermind 45250 points

    Olu,

    Thanks for your reply!

    I am going to send this to the customer and I will let you know if they have any further questions.

    Thanks again for your help!

    Richard Elmquist