• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 30 subscribers
  • Views 711 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLV320AIC32xx ADC input bandwidth

Steven Knudsen
Prodigy 70 points
Other Parts Discussed in Thread: ADS8866

Hi, and thanks for your consideration. 

I am interested in using the codec to do sub-sampling of a bandlimited signal, so need to know the input bandwidth of the ADC(s). Looking at the datasheet and application note I believe the BW is about 600 kHz, but no where I can see is it listed as a spec.

Thanks!

  • 0
    TI__Guru* 84915 points

    Hi Steven,

    Welcome to E2E and thank you for your interest in our products.

    The TLV320AIC32xx includes a stereo audio ADC, which uses a delta-sigma modulator followed by a digital decimation filter. The decimation filter has a -3dB bandwidth of 0.45fs. So, the sample frequency determines the ADC bandwidth (similar to DAC).

    I hope this helps you. If you still have questions, please let me know.

    Best regards,

    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 70 points
    Hi Luis.

    Thanks for the very quick response. However, this is not the answer. The sample frequency determines the bandwidth of the signal that comes out of the ADC, but I am interested in the input bandwidth. Consider, for example, the ADS8866. It has a small signal bandwidth of 30 MHz and a maximum sampling rate of 100 kHz.

    My application is sub-sampling; so, for example, with the ADS8866, I could sample a bandlimited signal < fs/2 = 50 kHz at any frequency up to 30 MHz. I want to do something similar with the TLV320 that is already part of an existing card I use.

    Rather than get an eval kit and test it, I'd just like to know the input bandwidth for the TLV.

    Does that help clarify things?

    Thanks,

    steven
  • 0 in reply to Steven Knudsen
    TI__Guru* 84915 points

    Hi Steven,

    Thank you for clarify the things.

    I made some tests with the codec evaluation board and it seems that it is limited to work with audible signals. I obtained a bandwidth of 25kHz approx.

    I hope this helps you. If you still have questions, please let me know.

    Best regards, 

    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 70 points
    Thanks, Luis.

    That would seem to imply there is a bandlimiting filter on the input, but that is not shown on the block diagram. Only the programmable gain amplifier is shown and I seriously doubt it is bandlimited to < 192 kHz.

    Can you describe the tests just so we can be sure that the codec cannot be used to perform subsampling?

    If I was setting up a test, I would configure the codec to sample at 192 kSps and input a sequence of tones, one at a time, at 12.5 kHz, (192 - 12.5) kHz, (192 + 12.5) kHz, (2*129 - 12.5) kHz, (2*192 + 12.5) kHz, ..., (n*192 - 12.5) kHz, (n*192 + 12.5) kHz

    where n is an integer > 0 and is increased until you can't see an output from the codec. All the outputs should be at 12.5 kHz since the signal folds due to sub-sampling.

    You may want to refer to electronicdesign.com/.../adcs-feel-need-speed or analog-eetimes.com/.../basics-of-adcs-and-dacs-part-1.html;news_id=207801388 to better understand what I am trying to do.

    I would like to reiterate that I fully understand that the output bandwidth is limited to 25 kHz; that doesn't need to be tests as far as my question is concerned.

    Thanks,

    steven