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DIX4192 RX input CMRR?

Jon Paul
Prodigy 50 points
Other Parts Discussed in Thread: DIX4192, DIT4192, INA149

Hello I am  on the AES Standards committee 02-02 for digital audio transmission.

As a part of the review and rewrite of AES 3-4 and AES 2id, this critical question has come up.

No TI  datasheets and app notes have  info on this:

AES/EBU is a differential transmission on a twisted pair. It is often used in a noisy EMI environment.

1. What is the topology of the input stages of the digital audio receivers such as DIX4192,  used for AES/EBU? eg differential pair? 2 hysteretic comparators?

2. What is the CMRR vs freq. of the input stages of the digital audio receivers such as DIX4192,  up to VHF frequencies used in broadcast eg 100...500 MHz?

3, As digital audio PHY is RS-422 or RS-485 compatible, same question for TI interface prodicts with a differential input.

These same questions apply to ANY TI audio part with a differential digital input.

4, For TI digital audio transmitters eg DIT4192, what is the output risetime min/max into a 110 Ohm load?

Any assistance will be greatly appreciated,


With Kind Regards,

Jon D. Paul, MSEE

V.P. Scientific Conversion, Inc.

  • 0
    TI__Expert 3110 points

    Hi Jon,

    I am working on answering your questions. Please bear with me as this is a very old part and the information is a little more difficult to locate compared to some of our newer parts.

    Regards,
    Mike Ulrich

  • 0
    Prodigy 50 points
    Mike many thanks, same question applies to any TI parts transmitting AES/EBU!

    Jon
  • 0 in reply to Jon Paul
    TI__Expert 3110 points
    Hi Jon.

    1. I cannot release the internal topology of our parts.

    2. CMRR is not data that we have. We usually do not run CMRR tests on differential input or output. The nature of a differential signal alomst guarantees the CMRR is good.

    3. The DIX4192 is RS422 compatible

    4. Again, this is not data we typically test for. Is there a specific way you would like me to test this to get you values that would help?

    Regards,
    Mike Ulrich
  • 0 in reply to Mike Ulrich
    Prodigy 50 points
    Hello Mike:

    1, I am not asking for the IC schematic, simply the form of the input circuit. RS-422 topology does not guarantee a differential input stage.

    2, Any Differential amplifier stage will have a curve of CMRR vs frequency. Without knowing the DC CMRR and breakpoint, the unit may have zero or tremendous CMRR at a particular frequency.

    For instance, Please see: the specs for TI ina149.
    or e2e.ti.com/.../dealing-with-rejection-instrumentation-amplifier-psrr-and-cmrr.aspx

    Or e2e.ti.com/.../dealing-with-rejection-instrumentation-amplifier-psrr-and-cmrr-part-ii.aspx

    As its impossible to make this test without access to the internal amp output pin, a simulation is the only solution I see.

    3, All AES/EBU compatible parts are RS-422 or RS-485 compatible.

    4, Info requested is to assist for AES Standards 3-4 and AES 2id revisions, now in discussion by WG 02-02N.

    5, Finally what is the Tr and Tf of the output when driving a 110 Ohm balanced load? When driving a100 m of AES/EBU or CAT 5 cable into a 110 Ohm loand?

    We are also in touch with other suppliers of Digital Audio interface ICs.
    In case you have no further way to get info, I will try to find the IC designers.

    With Kind Regards,

    Jon D. Paul, MSEE

    PS Can we please connect via email or Linkedin directly?
  • 0 in reply to Jon Paul
    TI__Expert 3110 points
    Hi Jon,

    I do not have the data you are requesting. However, I am willing to perform whatever test you wish to acquire this data. Can you detail out which tests you would like me to perform and I will get back to you with the results? I will be using the DIX4192EVM for my tests. Information on this can be found here: www.ti.com/.../DIX4192EVM-PDK

    Regards,
    Mike Ulrich
  • 0 in reply to Mike Ulrich
    Prodigy 50 points

    Dear Mike:You mentioned that this part is very old: What is the most up to date version, eg that handles 382 kHz?


    Suggested Test  Procedure:

    1, Place 110 Ohm bal load, probe with 1 GHz BW scope, differentially on output loaded by 110 Ohm.

    Check rise/fall-time with 192 kHz FS TX signal. Extract eye pattern and measure jitter of TX signal.

    2, Repeat #1 with a 100M length of CAT 5, CAT 5e, CAT6 and various so called "AES/EBU" cables eg Mogami, Canare, Belden 1800B, etc.

    Procedure: Connect  4192 output via balanced cable to a 110 Ohm load, repeat Tr, Tf, eye pattern and jitter test at BOTH 4195 output terminals and at end of cable at 100 Ohm R. 

    With Kind Regards,

    Jon Paul

    PS: Please see my AES 2003 and SMPTE 2014 papers. On our website at scientificonversion.com

    PPS: I have that same eval bd but was I unable to configure with the DIP switches (not under PC control) to get a simple 192 kHz TX signal.

  • 0 in reply to Jon Paul
    TI__Expert 3110 points

    Hi Jon,

    We do not have a part that handles 382kHz

    Additionally, since you would like so many tests performed I would like to help you get the EVM you have up and running. Do you have the device running at the lower frequencies? What register settings have you already tried? What are you using as your master clock?

    Regards,
    Mike Ulrich

  • 0 in reply to Mike Ulrich
    Prodigy 50 points

    Mike I found the board I have is from Cirrus Logic, I do not have the TI DIX4192.

    1. Can I get one as an eval sample or courtesy?

    2. May need a phone call to resolve the issues.

    3, If you get me a board I can do the tests. Otherwise you will need to do it.



    Kind Regards,

    Jon
    PS: How to continue this off the Forum?

  • 0 in reply to Jon Paul
    TI__Expert 3110 points

    Hi Jon,
    I have gotten the approvals to send you an EVM board. Do you have a preferred address for me to send it to?
    Also, I will put together a list of scripts for various settings for this board that I will send you.

    We prefer to keep questions on E2E so that if other uses have similar inquiries they can find the answers. If absolutely necessary to help set up the board, I can contact you via the email address you used to sign up for the forums.

    Regards,
    Mike Ulrich