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TMS320F28032: ADC output variation become larger

Part Number: TMS320F28032

Hi

 

Our customer is facing a trouble with ADC on F28032.

They guess that ADC output variation become larger when ambient temperature is changed.

 

-ADC gets DC (2.5V) signal, and 128 sampling data (256us sampling period with 2us cycle) are

 performed FFT processing.

-When ambient temperature be warmed or cooled (for the evaluation purpose by Hairdryer),

 ADC output variation become larger. And, it causes to failure in the market.

 

 

Q#1: Does the following thing is expected behavior?

     “ADC output variation become larger when ambient temperature is changed.”

 

Q#2: Customer use 60MHz clock (4.6MSPS).

     According to Errata, there are same issue related to ADC.

     Does above customer’s usecase much one of them?

Thanks and Best regards,

HaTa

  • Q#1: Does the following thing is expected behavior?

         “ADC output variation become larger when ambient temperature is changed.”

    Can you elaborate on what "variation" means to the customer? Is it referring to something like codespread where the samples appear to be affected by additional white (random) noise, or is it that the samples are drifting as a group away from the room temperature average?

    I would not be surprised to find that the samples drift as a group in response to temperature variations. This is generally expected to take place within the range of datasheet Min and Max errors.

    Q#2: Customer use 60MHz clock (4.6MSPS).

         According to Errata, there are same issue related to ADC.

         Does above customer’s usecase much one of them?

    Yes, I would advise the customer to implement the suggested workarounds for all documented advisories in the Errata.

  • Hi tlee

     

    >>Q#1: Does the following thing is expected behavior?

    >>       “ADC output variation become larger when ambient temperature is changed.”

     

    >Can you elaborate on what "variation" means to the customer?

    >Is it referring to something like codespread where the samples appear to be affected

    >by additional white (random) noise, or is it that the samples are drifting as a group away from the room temperature average?

    >I would not be surprised to find that the samples drift as a group in response to temperature variations.

    >This is generally expected to take place within the range of datasheet Min and Max errors.

     

    Which error are you referring?

    Is it "Offset error" or "Overall gain error" at chapter 9.9.2.1.3. in

    www.ti.com/.../tms320f28032.pdf

     

     

    >>Q#2: Customer use 60MHz clock (4.6MSPS).

    >>       According to Errata, there are same issue related to ADC.

    >>       Does above customer’s usecase much one of them?

     

    >Yes, I would advise the customer to implement the suggested workarounds for all documented advisories in the Errata.

     

    If it meets the errata conditions, can the value fluctuate suddenly at some point, even though it's usually working pretty well?

     

    Thanks and Best regards,

    HaTa

  • Which error are you referring?

    Is it "Offset error" or "Overall gain error" at chapter 9.9.2.1.3. in

    By Min and Max errors, I was referring to the Offset, Gain, and Linearity errors from the datasheet.

    If it meets the errata conditions, can the value fluctuate suddenly at some point, even though it's usually working pretty well?

    Possibly.  However, you still have not clarified what "variation" means.

  • Hi tlee

    By Min and Max errors, I was referring to the Offset, Gain, and Linearity errors from the datasheet.

    Are they the parameters in the red box below?

     

  • Yes, and INL.