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AM335x ACD Analog input and GND referece

Yaniv G
Prodigy 30 points

Hi,

For using AM335 ACD , AIN0-AIN7, the analog input should be reference to same ADC GND ?

In the Starter kit design the analog signal reference to DGND (page 9).

Thanks.

  • 0
    TI__Guru 62945 points

    Yes, the ground reference for analog inputs AIN[7:0] is VSSA_ADC.  However, the voltage applied to VREFN defines the minimum voltage of the ADC input voltage range and the voltage applied to VREFP defines the maximum voltage of the ADC input voltage range.

    The EVM SK is using the ADC in touch screen mode where the AIN[3:0] inputs/outputs are connected to a resistive touch screen.  In this touch screen use case the ADC input voltages are self generated when two of the AIN[3:0] terminals operate in output mode while also operating as voltage reference inputs to the ADC INT_VREFP and VREFM inputs.  The other two AIN[3:0[ terminals operate as inputs and connect to the ADC INP and INM inputs.   Therefore, all voltage references are internal to the ADC or Touch Screen Controller (TSC) and do not need to be referenced to VSSA_ADC.

    The unused AIN[7:4] inputs are conneccted to VREFN which is connected to VSSA_ADC through R72. 

    Regards,
    Paul