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ADS1263: ADS1263 sampling 2 analog sources and convert range improvement, etc.

Dmytro Rahozin
Prodigy 40 points
Part Number: ADS1263
Other Parts Discussed in Thread: ADS127L11, ADS127L18, ADS127L14

Hi, gentlemen,

      I have a question after my first light with ADS1263. Maybe question partially will look silly but I'm originally a computer scientics with some old backgroud in electronics.
      My 1st question:
      1) ADS1263 has many commuted inputs. Of course we wonder if we can sample 2 differential channels simultaneously switching these channels inputs for ADC1 in ADS1263. The problem is than we need 10k SPS from both channeds, so we need to switch channels with 20K/second rate. Ok, in ADS1263 ref. manual I see that ADC setup time is 52us. As setup time is unavoidable, it limits switching rate down less than 5K/sec.
       Am I right in my calculations?

      2) I also looked precisely into ADS1263 doc and see that real noise-free bits are something like 21-22 for 10kSPS. It's good enough, but....
      The question is: can you recommend several ADCs from TI product line, with precision 24-28 bits at 10kSPS, with price less than $15-20 for 1K units. Low-noise pre-amplifier inside an ADC looks ok, as it can limit necessary number of bits under 24. One of case I've seen is ADS127L11, 24bit, with 22 noise free bits on 10kSPS, for our signals it requires pre-amplification, that's OK. But maybe there are other possibilities from TI product lines.

      Thank you,
        D.

  • 0
    TI__Mastermind 37310 points

    Hi Dmytro,

    The primary apps engineer, Bryan, will come back next Monday, please allow a delay on his response.

    BR,

    Dale

  • 0 in reply to Dale Li
    Prodigy 40 points

    Thank you!
    Will have time to review TI product lines. :)

  • 0 in reply to Dmytro Rahozin
    TI__Mastermind 37310 points

    Hi Dmytro,

    Thanks for your patience.

    BR,

    Dale

  • 0 in reply to Dale Li
    Prodigy 40 points

    Hi,

    Did your primary app enginner already returned?

  • +1 in reply to Dmytro Rahozin
    TI__Mastermind 37371 points

    Hi Dmytro Rahozin,

    Thanks for the reminder

    Dmytro Rahozin said:
    Of course we wonder if we can sample 2 differential channels simultaneously switching these channels inputs for ADC1 in ADS1263. The problem is than we need 10k SPS from both channeds, so we need to switch channels with 20K/second rate

    The ADS1263 has two ADCS inside (ADC1 and ADC2). However, ADC2 can only sample up to 800 SPS, so you would not meet the timing requirements using both ADCs. If you used ADC1 and multiplexed between channels, then you would be subject to the latency times specified in Table 9-13 in the datasheet. For example, the fastest you can possibly sample when multiplexing between channels is 207us (@ 38.4ksps), which is the equivalent of 4.8kHz.

    You can review this app note for more information about conversion latency in multiplexed delta sigma ADCs: https://www.ti.com/lit/an/sbaa535/sbaa535.pdf?ts=1709134616985

    Dmytro Rahozin said:
    The question is: can you recommend several ADCs from TI product line, with precision 24-28 bits at 10kSPS, with price less than $15-20 for 1K units.

    As you noted, the ADS127L11 is likely the best option here for >20 bits at 10kSPS. Another option is the ADS127L14 or ADS127L18, which are simultaneously sampling versions of the ADS127L11 i.e. basically multiple L11's in the same package. You can theoretically lower the noise by sampling the same input on two channels, and then averaging the results of those two channels. Since you have two inputs to sample, you could use the L14 and apply one signal to channels 1 and 2, and the other signal to channels 3 and 4. This is going to be the best option for high speed, higher resolution sampling

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 40 points

    Thank you very much and forgive me my impolite reminder.
    I'll recheck ADSADS127L11 once more - I have read ADS1271L11 manual but I was not sure if it is the good choice.

    Thank you!

  • 0 in reply to Dmytro Rahozin
    TI__Mastermind 37371 points

    Hi Dmytro Rahozin,

    I'm glad we could confirm that this is the right device to consider for your application.

    Also, I should have mentioned that the L14 and L18 (4- and 8-ch simultaneous sampling versions) have not released yet, but should be online in the next week or so. The evaluation module is already there if you want to take a look at it: https://www.ti.com/tool/ADS127L18EVM-PDK

    -Bryan