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TMS320F2808: Offset Error Correction

DO-Pro
Intellectual 610 points
Part Number: TMS320F2808


Hi,

I'm going through details of Offset Error Correction procedure outlined in TMS320x280x DSP Analog-to-Digital Converter (ADC) Reference Guide, SPRU716D, section 1.9, Offset Error Correction, p.31. This procedure recommends to begin correction process with having about 20 conversions of ADCLO reference. I couldn't find any information in this guide as to how to configure ADC for such a conversion so my question is as follows.

Q: Does 2808 device have any internal resources that would assist in temporarily connecting ADCLO reference to the input of the ADC channel for purposes of this conversion or should I simply treat ADCLO as an external signal and permanently sacrifice one of the available ADC input pins to connect ADCLO reference to the ADC module externally?

Since some other TI devices provide internal dedicated resources for the said purpose, I expected 2808 to include similar functionality as well.

Please clarify this moment for me.

Regards, Michael

  • 0
    TI__Prodigy 540 points
    Hi Michael

    Just to clarify, are you seeing an Offset error on the device? In most applications, the production trims should be sufficient. Those trims should get pulled in via the ADC_Cal routine and populate the registers.

    If you do see a need for correction, you would externally short any of the ADC channels to ADCLO. Are you seeing a needs to correct repeatedly? Usually, repeated corrections are not needed per device, so an ADC channel need not be permanently connected to ADCLO.

    -Nabil
  • 0 in reply to Nabil Saheb
    Intellectual 610 points

    Nabil,

    Thank you for your response. No, I currently don't have a need to calibrate. I'm in the schematic design stage and simply tried to determine what means are available to me to do the system level calibration and whether or not I have to allocate additional hardware resources for the purpose.

    Your explanation fully covers my current needs.

    Regards, Michael

  • 0 in reply to DO-Pro
    TI__Prodigy 540 points
    Michael

    Since you're still in the design phase, some more items to keep in mind:

    -Have a look at the datasheet, it has numbers on what you can expect with and without hardware trimming for Offset error. You may need to permanently assign an ADC channel for correction if your application requires
    - Have a look at the Application Report for ADC Calibration for TMS320280x devices here: www.ti.com/.../spraad8

    -Nabil