ADG1613 - how to handle the GND pin in mixed signal designs?

I'm about to use the ADG1613 in a single supply audio / mixed signal design. Vss is connected to the analog ground (0V), Vdd to the analog power rail (12V in this case). There also is a virtual GND for the opamps of the circuit (6V). The digital part consists of a microcontroller with a seperated 3.3V supply.

Now I'm wondering about the GND pin of the ADG switch. Should it be handled as a return path for the logic control inputs like a "digital ground" pin on an ADC? The datasheet entry is: "Ground (0V) Reference", which sounds more like a reference point where analog and digital ground is connected.

So I'm a little confused, may be someone can help me with this question?

Thanks a lot,

Mathias

  • 0
    •  Analog Employees 
    on Jan 7, 2016 7:02 PM

    Hi Mathias,

    You mentioned that VDD is from the analog power rail, correct? The ADG1613 GND pin should be connected to the 0V reference ground, analog power ground in your case.

    Best Regards,

    May

  • Hi May,

    thanks for your answer. Yes, VDD is from the +12V analog power rail, VSS is analog ground (0V). So if that GND pin on the ADG switch have to be at 0V, I can connect it to the digital or analog part of the GND plane. I don't know how this pin is connected internally, but I think it's a voltage reference point for the logic control inputs. So if - in my case - the input's logic level is controlled from a micro controller, wouldn't it be better to connect it to the digital GND? I'm a little afraid of getting EMI problems in the analog part of the circuit when the return path of the (digital) current is  running through the analog ground.

    Kindest Regards,

    Mathias

  • GND and Vss of the ADG1613 are not internally connected.

    The GND pin is the reference for the level shifters inside the part to actuate the switches.

    Your analog and digital ground will likely be connected somewhere in the system. It might or might not be a good idea to make the connection at the ADG1613.

    Like May, I would suggest you connect both the GND and VSS pins to the analog ground plane.

    Your worry about return currents are probably unfounded as the inputs draw almost none. You can reduce the effect of capacitive coupling by inserting series resistors into the control lines to filter them.

    Klaus

  • 0
    •  Analog Employees 
    on Jan 10, 2016 7:18 PM

    Hi Mathias,

    I agree with Klaus. You see, GND pin is the reference of the level shifters and the power supply of the device.

    It is a good practice to connect the GND pin of the ADG1613 to the analog ground and properly power-up the device. To control the logic pins (A0, A1, A2, EN), you may connect them to a microcontroller as long as the analog and digital ground will be connected at some point in the system to create a close loop for current flow.

    Best Regards,

    May

  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:19 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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