• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 46 subscribers
  • Views 315 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.

ADS1278: Analog bandwidth and usage for undersampling application?

Ondrej Daniel
Prodigy 50 points
Part Number: ADS1278

Dear TI,

I am looking for space qualified multi-channel ADC. I need to sample very low bandwidth signals (carrier waves) with carrier frequencies of ~10 MHz.

I am wondering whether ADS1278 (which has maximum sampling rate of 144 kHz) could be used to sample these ~10MHz signals in under-sampling mode.

What would be your opinion about this idea?

Have you characterized the input analog bandwidth of this chip up to 10 MHz (or even more)?

Is it in general a bad idea to use sigma-delta ADC for doing undersampling?

(I am considering this particular ADC, since you also provide it in a space-qualified version, and we are targeting a space application on Medium Earth Orbit. Unfortunately, I could not find many multi-channel (ideally 8 channels, 4 would be acceptable) space-qualified ADCs with sampling frequencies allowing to directly sample these ~10MHz signals.)

Thank you very much!

Ondrej

  • +1
    TI__Mastermind 46200 points

    Hello Ondrej,

    We do not have any information or test data to support under-sampling.  In theory, if you set the modulator to 5MHz (input clock to 20MHz); you would get an output data rate of 78ksps that would pass a signal at 10MHz carrier and up to 39kHz.  However, you would likely see quite a bit of distortion, and the maximum input signal would need to be reduced by 20dB to 40dB to avoid modulator saturation, so your SNR will not be very good as well.

    This is not something that we can recommend.  TI has high speed, space rated -SP and -SEP ADCs that can be used to measure such a signal, but these would be pipeline based, not delta-sigma.

    Regards,
    Keith Nicholas
    Precision ADC Applications