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ADS1210: ADC output data is shift

Takumi Suzuki1
Mastermind 8610 points

Part Number: ADS1210

Hi,

Let me ask you a question about data shift phenomenon of ADS1210 as below.

The ADC output code is shift (red circle) as following graph when input is adding from 1mv to 1.4mV to ADS1210.

Have you ever experienced this kind of phenomenon about delta-sigma ADC?

Will you give me any advice to solve this problem? It would also be welcome the general advice.

By the way, there always not happen this problem and there may be around 1.0% happened of total products. (around 25Kunits)

Thank you for your support in advance.

Best Regards,

  • 0
    TI__Guru** 113765 points

    Hi Suzuki-san,

    The ADS1210 is susceptible to a number of slow ramp issues depending on mode of operation.  From this particular plot there appears to be a pattern at approximately every 210 codes.  As we don't have the raw data throughout the entire region, it is difficult to say if there is a specific pattern at those points.

    I have seen dead zone issues in the past with slow ramps where a small range of input voltage will hold the ADC output code at the same or nearly the same value.  This can be related to the amount of available charge while sampling and comparing to the reference.  In the end the modulator is repeating the same series over and over resulting in a stuck output code.  In this case there seems to be something different and could be related to a stuck bit in the conversion result register.  It is difficult to say for sure what might be happening or what to do to resolve the issue.  It may be something related to process variation.  As this device is about 20 years old and the original process to build the device is no longer available we can no longer run simulations to help diagnose these types of issues.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Mastermind 8610 points

    Hi Bob-san,

    Thank you so much for your kind reply!!

    Your advice would be very helpful for me.

    By the way,

    Let me ask you one more, about the process of ADS1210, the currect ADS1210 device is made by old process(around at the time of 1997) or another new process?

    Best Regards,  

  • 0 in reply to Takumi Suzuki1
    TI__Guru** 113765 points

    Hi Suzuki-san,

    The ADS1210 was a Burr-Brown design that was originally fabricated at an OKI fab.  This fab no longer exists, and was ported over to a TI fab in January 2011.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Mastermind 8610 points

    Hi Bob-san,

    Thank you so much !

    Best Regards,