• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 46 subscribers
  • Views 287 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.

ADS1282: noise floor spike

Iouri Markin
Intellectual 650 points
Part Number: ADS1282
Other Parts Discussed in Thread: ADS127L11

Tool/software:

Hello,

We are using ADS1282 ADC, sampling rate 64KHZ; data size 24 bit. Shorting ADC input to middle ground point(2.5VDC).

Trying to collect noise floor.

Getting following plot, please see bellow. Our application required bandwidth is from 10HZ-12KHZ.

Using spectrum analyzer we probed entire board, power lines, reference voltages and all lines are "clean".

Can you please advise what can cause this (8KHZ) peak, and how we can rid off?

Thank you for all your support.

Regards,

Iouri

  • +1
    TI__Mastermind 46780 points

    Hello Iouri,

    You are seeing the chopping frequency at 8kHz.  The ADS1282 is only intended to be used for input frequencies up to 2kHz and additional filtering should be used to reject any frequency above 2kHz.  This is why the datasheet only specifies noise performance with data rates of 4ksps and lower.

    You could, in theory, create a digital notch filter to get rid of the 8kHz noise, but you will still have the increased noise floor as shown in Figure 32.

    For best noise performance at 64ksps or higher data rates, I suggest looking at the ADS127L11.  This ADC has many digital filter options and will provide very good performance in the bandwidth you are looking at.  The ADS127L11 does not include an internal PGA, but you can easily add an external PGA if input gain is needed.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Intellectual 650 points

    Hi Keith,

    Thank you for the detailed answer, let me run this by the team before closing

    regards,

    Iouri