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ADS1115 - GND and VDD are analog or digital?

andre.robotokogaku
Intellectual 440 points
Other Parts Discussed in Thread: ADS1115

Hello there,

I'm evaluating the possibility of using ADS1115 16-bit ADC in my new design. I searched in the datasheet but didn’t find any specification whether to connect GND and VDD pins to analog or digital power circuits.

Normally ADCs have separated AGND and DGND pins, but it’s not the case with this IC.

Has anyone here already laid out a PCB with this ADC?

Thanks in advance,

André Araujo.

  • 0
    TI__Guru 55466 points

    Hello Andre,

    For the voltage supply connection, the general recommendation is to use a 0.1uF bypass capacitor in close proximity to the supply pin.  The 0.1uF capacitor help to supply the momentary burst of extra current needed from the supply.  In general, you may want to use a quiet, low noise voltage supply.

    You may refer to the ADS1115EVM for an example.  The PCB board has a split Ground board layout where the GND pin of the ADS1115 is connected to the analog Ground plane.  A general recommendation is to route the analog signals away from the digital signals.

    Please find the ADS1115EVM schematic and PCB plots attached as an example.

    Below is also a link with board layout recommendations.

    http://e2e.ti.com/support/data_converters/precision_data_converters/w/design_notes/1302.general-pcb-layout-questions.aspx

    Thank you and Best Regards,

    Luis

    ADS1115EVM schematic and board layout plots:

    8865.ADS1x15EVM_Gerber_Plots_B.pdf

    1682.6511174_ADS1x15_SCH_B.pdf

  • 0 in reply to Luis Chioye
    Intellectual 440 points

    Hello Luis,

    Thanks for the quick reply!

    In summary: VDD is analog circuit, must have a 0.1uF cap. near the pin; GND is analog circuit; keep digital pins (SDA, SCL, ALERT/RDY, ADDR) apart from analog pins.

    Regards,

    André Araujo.