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CCS/TMS320F28379D: ENOB and resolution of Sigma-delta module

lio messi
Expert 1185 points
Part Number: TMS320F28379D

Tool/software: Code Composer Studio

Hi community!

Excuse me if it is a stupid question! What is the difference between "ENOB (effective number of bits)" mentioned in the AMC datasheet and "x-bit resolution of the modulator" in TRM? 

Could you please explain me the definitions and way to designating them in the projects and system designs?

Thanks

  • 0
    TI__Guru 55700 points
    Messi,

    x-bit of resolution mentioned in TRM shows the minimum / maximum digital value for a given filter type / OSR configuration. TRM doesn't mention ENOB because it also depends on SD-modulator frequency and order of modulator.

    ENOB mentioned in SD-modulator datasheet is a better representative of resolution than TRM tables. Please use that.

    Regards,
    Manoj
  • 0 in reply to Manoj Santha Mohan
    Expert 1185 points
    Thanks for your reply
    So are the "settling time of filter" mentioned in the AMC datasheet and the "latency of filter" mentioned in the TRM same?
    What is the meaning of "The delay time of the sinc filter with a continuous signal is half of its settling time." mentioned in the AMC datasheet? I mean what is the "delay time" and when does it happen?
    best regards
  • 0 in reply to lio messi
    TI__Guru 55700 points
    Lio,

    Yes, settling time mentioned in AMC datasheet is the "Latency of Sinc filter" mentioned in TRM.

    Delay time mentioned is actually ambiguous. When a step input is provided to SD-modulator it takes a specified amount of delay time (which C2000 TRM calls latency of sinc filter) to get the digital filter output to steady state which represents the correct digital filter output for corresponding analog input. But, instead of step input, if the analog input is marginally varying the digital filter output steady state time is much lesser compared to setting time (latency of sincfilter).

    Regards,
    Manoj
  • 0 in reply to Manoj Santha Mohan
    Expert 1185 points
    Thank you Manoj for reply and your help
    regards