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PCM6240-Q1: Input Attenuator and PGA and SBAC263 Questions

Toshiyuki Murakami
Prodigy 90 points
Part Number: PCM6240-Q1
Hello.
Ask about the PCM6240.
(1) For Input Attenuator and PGA, does the Gain variation change for each channel? Or will it be the same? Also, does it change in the LOT of the IC, or does the variation occur regardless of the Lot?
(2) I'm using SBAC263 to calculate the rext value, but the tolerance for R1, R2, R3 is ±20%, and is it acceptable to specify a min value rather than a typ value?
     What is "PGA amp INCM" in Device parmeters?
     Is "Max Vcm" in Device parmeters a Peak value? Or is it an RMS value?
We are waiting for your answers.
  • 0
    TI__Mastermind 19495 points

    Hi,

    (1)The attenuator and PGA gain values of each channel will change independently based whether high or low swing mode is chosen. I suppose that yes, there will be some variation between different lots of ICs. why do you ask this?

    (2)where are you finding "device parameters" I cannot find this field in any PCM6xx0 documentation. Where did you find the R1,R2,R3 tolerance as 20%?

    Max VCM (maximum common mode voltage) is a DC specification. 

    Regards,

    Arthur

  • 0 in reply to Arthur Brown
    Prodigy 90 points
    Hello Arthur. Thank you for your answer.
    Reply about each.
    (1) 
    I want to confirm whether gain variation in the block until it reaches the ADC block between channels occurs in different lots of ICs, or for each IC alone. For example, whether it fluctuates ± 1% in Channel 1, ± 5% in Channel 2, and so on. Do you have specific numbers at your company?
    (2) 
    It is described in the application note SBAC263 of pcm6240.
    https://www.tij.co.jp/jp/lit/zip/sbac263
    I would like to ask you again about the maximum VCM. Is it ok to say that it is the maximum value of the waveform in the DC specification?
    Regards,
  • 0 in reply to Toshiyuki Murakami
    TI__Mastermind 19495 points

    Hi Toshiyuki,

    I asked around to the design and systems team and this isn't a specification that was noted. however in general the attenuator and PGA will configure themselves to give the proper signal amplitude for the internal ADC. the gain variation due to process shouldnt need your direct consideration.

    the Max VCM is the common mode voltage at the inputs. this is the DC voltage that the input signal is centered around. 

    for example if the common mode voltage is 7.1V, and the signal is 2Vpp. then the peak voltage seen at the input pins would be 8.1V

    Regards,

    Arthur