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ADS1261: Conversion time

TATSU Numa
Intellectual 800 points

Part Number: ADS1261
Other Parts Discussed in Thread: ADS131E04, ADS131M04

Hi Team

 Let me ask about the conversion time.

① Customer set the ADC conversion mode to pulse (one-shot) conversion and just want to shorten the conversion time. (Hope is 75us or less)
Therefore, they set the Data Rate to the maximum 40000SPS and measured the conversion time, which was approximately 200us.
For pulse (one shot) conversion, would you please take this much conversion time even with the minimum settings?

② If there is a product that uses ΔΣ type ADC and has a conversion time of 75us or less in pulse (one-shot) conversion mode, would it be possible for you to suggest it?

best regards

TATSU

  • 0
    TI__Guru 55271 points

    Hi TATSU Numa,

    Can you please post the customer name in the Notes section of the Thread Tracking Toolkit?

    The ADS1261 first-conversion latency is given in Table 8 in the datasheet. I have copied this table below. Note that at 40kSPS the latency for the first conversion is 179us, which is approximately what the customer saw.

    Also note that this only applies to the first conversion. The next conversion would be available at ~1/data rate, or 25us in the case where data rate = 40 kSPS. So if the customer is sampling one channel repeatedly (using continuous conversion, not pulse convert mode), then every data except for the first data will be available in ~25us. If the customer uses pulse convert mode for each data, then each data will be subject to the time in Table 8

    You and the customer can learn more about conversion latency in delta-sigma ADCs using this app note: https://www.ti.com/lit/an/sbaa535/sbaa535.pdf?ts=1696515394554

    Some questions for you to help us identify the correct ADC to recommend in case the ADS1261 still will not work for the customer's application:

    • Will the customer sample the same channel many times, or do they want to multiplex through multiple channels?
    • Why does the customer need to use pulse convert mode?
    • Does the customer need any of the other features of the ADS1261?

    -Bryan

  • 0 in reply to Bryan Lizon86
    TI__Intellectual 800 points

    Hi Bryan 

    Thank you for your response.

    And, Let me answer to following question.

    Then, are there any appropriate devise?

    • Will the customer sample the same channel many times, or do they want to multiplex through multiple channels?

               =>Customer will use Multiplexing  through multiple channels. And, customer needs 4ch or more.

    • Why does the customer need to use pulse convert mode?
    • Does the customer need any of the other features of the ADS1261?

                =>Also, an excitation current source is not required, but there is nothing else required beyond the features included in the ADS1261.　

    Best regards

    TATSU

  • 0 in reply to TATSU Numa
    TI__Guru 55271 points

    Hi TATSU Numa,

    Can you please post the customer name in the Notes section of the Thread Tracking Toolkit?

    -Bryan

  • 0 in reply to Bryan Lizon86
    TI__Intellectual 800 points

    Hi Btyan

    I wrote the customer name

    best regareds

    TATSU

  • 0 in reply to TATSU Numa
    TI__Guru 55271 points

    Hi TATSU Numa,

    The customer might consider using a simultaneous sampling ADC then, if they want to measure many channels in 75us

    For example, the ADS131M04 or ADS131E04 could be good options. These devices have 4 ADCs in each package, which means there is no multiplexing from one channel to the next. Instead, al 4 inputs are sampled at the same time, and data is available for all 4 channels at the same time. This will allow the customer to sample much faster

    Let me know if these devices are a good option for the customer

    -Bryan