• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 1011 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

ADS131 Low Frequency Noise

Jan Burgemeister
Intellectual 565 points
Other Parts Discussed in Thread: ADS131E04, ADS1271, ADS131E08

Hi,

I am using the ADS131E04 in a design where inputs from 0.2 to 2000 Hz are to measured over a wide dynamic range. I observed an increase of the ADS131 noise voltage at low frequencies (< 10 Hz). The input circuit can be excluded as a noise source since I got the same noise with inputs shorted (MUXn = 001). I have also tried an external low-noise reference without improvements. Is there any overall spectral noise data available for the device? Can I improve low-frequency noise by changing the external components?

  • 0
    TI__Mastermind 23235 points
    Hello Jan -
    How are you observing the data? Have you tried increasing the number of points in the analysis? A small number of points in the FFT can contribute to a perceived increase in lower frequency components that aren't actually there.
    As to the question about availability of noise data, we will need to check and get back with you.

    If you can provide or would like us to review your design, you can post it or send it to pa_deltasigma_apps<at>ti.com (replace <at> with @)
  • 0 in reply to Greg Hupp
    Intellectual 565 points

    Thank you, Greg.

    I am measuring peak and RMS values by an MSP430 with variable IIR filters. I noticed no problem with a 10 Hz high pass. With a 1 Hz high pass noise is about 3 times higher than in a very similar design using the 24 bit ADC ADS1271.

  • 0 in reply to Jan Burgemeister
    TI__Mastermind 23235 points
    Hello Jan -
    So the ADS1271 and ADS131E08 are still very different design in terms of internal functionality. The AD1271 draws a lot more power and therefore should have a better noise performance.

    One quick question - What is the value of CONFIG2 that you are writing?
  • 0 in reply to Greg Hupp
    Intellectual 565 points

    Hello Greg,

    the ADS131 is very nice for small battery operated multichannel instruments because of its integrated programmable amplifier, low supply current and good price. According to TI it was designed for power monitoring - may be I just expect too much when I use it for low frequency / low magnitude signals. Anyway it would be interesting to have spectral noise data for comparison.

    I write CONFIG2 with 0xE03.

  • 0 in reply to Jan Burgemeister
    TI__Mastermind 23235 points
    Hello Jan -
    The ADS131E08 should be OK for use as a general ADC; the primary application is promoted/intended as power monitoring.

    With respect to the CONFIG2 register, you are away that the registers are only 1 byte (8bits) correct? Hopefully the 0xE03 is a typo, but if not, it may be that you are writing larger values and therefore inadvertently programming the part incorrectly.

    In terms of additional data, we can certainly see what we have but the time-domain plot in Figure 3 and FFT plot of Figure 10 in (in the datasheet) illustrate that there shouldn't be any low frequency noise issues. Figure 3 is taken across 10 seconds, so if there was low frequency noise you would expect the data to wander a little more that it shows. Figure 10 shows that there is no significant increase in the low frequency noise floor.
  • 0 in reply to Greg Hupp
    Intellectual 565 points

    I'm sorry, I write CONFIG2 with 0xE3.

    Thank you anyway.