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AM335x TSC/ADC reference manual

Jan Lellmann
Prodigy 50 points

I could not find the AM335x TSC/ADC reference manual on the website, is there a dedicated manual or is it only the short section in the AM335x TRM?

Specifically, I am trying to drive the ADC in differential mode, but with 0.2V on the differential pair I am getting erratic measurements around 0.9V with obvious bit errors. The single-ended mode appears to work fine.

  • 0
    TI__Mastermind 26215 points

    Jan,

    I will double check Momday ,but I am not aware of any dedicated TSC/ADC reference manual.

    We have also this wiki here:

    http://processors.wiki.ti.com/index.php/AM335x_ADC_Driver's_Guide

  • 0 in reply to Rogerio Almeida
    TI__Mastermind 26215 points

    I have checked and there is no specific manual for the ADC. You have the TRM and the wiki above.

     

    regards

     

  • 0 in reply to Rogerio Almeida
    Prodigy 50 points

    Hmm, ok. Maybe one particular question I cannot find an answer to: In order to run the ADC in differential mode, does it need a negative reference voltage? I am trying to run it in differential mode with 0V and 1.8V as negative and positive reference, but this does not seem to work at all, I get tons of conversion errors/outliers. Single-ended mode works fine.

    What would I have to supply? -1.8V and +1.8V? Or -0.9V and +0.9V? Is negative voltage on the negative reference pin or on the ADC input allowed at all? I tried to get this from the absolute maximal ratings in the data sheet, but did not find any information about this.

  • 0 in reply to Jan Lellmann
    TI__Guru 63605 points

    The AM335x Data Sheet defines the voltage limits of VREFP and VREFN in Table 3-17. 

    VREFP must be between [(0.5 * VDDA_ADC) + 0.25] and VDDA_ADC.

    VREFN must be between 0 and  [(0.5 * VDDA_ADC) - 0.25].

    Regards,
    Paul

  • 0 in reply to peaves
    Intellectual 970 points
    Hi,

    I have additional question regarding common mode voltage on the REF Inputs.

    Could someone comment this statement:

    "The voltage being applied to VREFP and VREFN should follow the requirement defined in TSC_ADC Electrical Parameters where VREFP + VREFN = VDDA_ADC which is 1.8 volts. If 1.5 volts is applied to VREFP, VREFN should be 0.3 volts (1.8 volts - 1.5 volts) to meet this requirement. The common mode voltage of these two pins should always be VDDA_ADC/2."

    If this is truth, what does it mean?

    For example, if VREP = 1.25V and VREFN = 0V, system will not function?

    Br,
    Josko