ADS1293: ADCmax

Part Number: ADS1293

Hi,

I am designing an application based on ADC1293.

I would like to use ADCmax as a direct function of R2 and R3, that is without referencing the tables 8,9,10 and 11.

Does such an equation exists ?

In relation with this question, how is it possible to explain the values for ADCmax found in these tables, e;g 0x8000 for Pace Channel and R2=4 ?

Thanks for your attention

Georges Masquelier

  

  • Hi,

      Are you referring to the Programmable Digital Filters?

      Would you please clarify and provide more info about what you mean by used ADCmax as a direct function of R2 and R3 without referencing the tables mentioned?

      Do you want to bypass the digital filters?

      According to the ADS1293 datasheet, those Decimation filters/digital filters cannot be bypassed as they are part of the ADC architectures to help ensure/maintain the performance and thus ADCmax depends on the digital filters configurations.

    For your e.g. question -

    Take Table 8 as example and reference,

    For PACE CHANNEL, if R1, R2 and R3 are set to 1, 4 and any, respectively, then, the Max ADC output code(i.e. ADCmax) can be seen/expected will be 0x8000 for PACE channel.

    For ECG CHANNEL, if R1, R2 and R3 are set to 1, 4 and 4, respectively, then, the Max ADC output code(i.e. ADCmax) can be seen/expected will be 0x8000 for ECG channel.

    Thanks.

  • HI,

    I receive correctly the output of the Programmable Digital Filters, that is ADCout..

    To calculate the differential input (e;g IN1-IN2) I need the ADCmax relative to my config.

    We find this parameter in the tables mentioned.

    My wish is to get ADCmax directly via a function of R2 and R3(if ECG) and NOT by loockup in these tables.

    Is that possible ? 

    Relative to ADCmax all the 4 tables are identicals. ADCmax is not a function of "fs" nor R1, is it possible to explain why ?

    Thanks

  • Hi Georges, 

    Forgive us for the delay, the USA is on holiday until Tuesday. We'll have a response for you then. 

    Kind regards,
    Nick Z

  • Hi Georges,

    Let me understand you correctly. When you say a "function", do you mean that you need a "equation" similar to equation (13), so that you can simply throw in the R1, R2 and R3 and returns the corresponding ADCmax?

    TI doesn't have that, so customer may need to code look-up table(e.g. switch or if) to use the appropriate ADCmax.

    TI cannot disclose the designers ideas and concepts related to that.

    Thanks

  • Hi,

    Thank you for your reply.

    I understand that you cannot explain the details of your products.

    The transfer fct of a CIC filter being related to R*M, and R1*M being constant (4), I understand that ADCmax is not a function àf R1.

     But for the rest, that is : ADCmax(R2) and ADCmax(R2,R3), I regret that you cannot explain them to me.

    Thanks.

  • Hi Georges,

    May I ask why do you need those info?

    TI has the reserved right to decide what info to be shared and disclosed.

  • Hi Yang,

    I am an automation engineer _retired_.

    My actual _personal_ project is to design a PLC (Programmable Lgic Ctrl) based on ARM Cortex M4F and a QK kernel (Miro Samek).

    One of the many tasks embedded in my PLC is based on ADS1293.

    Then you see I am a passionated developer ...

    It will be a pleasure for me if you could explain a bit the internals behind the famous ADCmax.

    Thanks a lot for your understanding.

  • Hello Georges, 

    Chien, our resident lead for this device is out today. He'll get back to you Friday. 

    I can look to get you a answer, but tracking down the right experts might take up to a week.

    Kind regards,
    Nick Z

  • Hi Georges,

     Sorry for the long wait and thanks for the patience.

     After discussion with the team, TI really cannot disclose further detail regarding to this.

     If you may have any other question, feel free to open another ticket.

    Thanks