AD4112: Isolation and Grounding

I'm using an AD4112 for measuring +/-10V signals.

I plan on using:

5V AVDD

0V AVSS

3v3 IOVDD

0V DGND

Onto the questions:

1a) If I use single-ended mode, can I get a true +/-10V bipolar signal in?  This would be the same as Figure 1b in this document, is that correct? https://www.analog.com/media/en/technical-documentation/product-selector-card/2pb_sarinputtypesfb.pdf

1b) In single-ended mode, the signal is VINx-VINCOM for each channel.  Is this correct?

2a) Do we need isolation like the ADuMxxx (from the evaluation board) if the analog signal's electronics are also on the same ground as our electronics?  In this case, VINCOM = AVSS = DGND = 0V.

2b) When do we need to use DC/DC isolation for this chip?  Under what conditions?

3) If AVSS = DGND, do they need to be connected in a "star configuration" or "star ground" layout?  Or can they just be directly coupled to each other?  On the evaluation board it looks like the DGND and AVSS are connected simply with a via.

Thanks in advance.

  • 0
    •  Analog Employees 
    on Apr 28, 2020 3:09 PM

    Hi Benjamin, 

    1) a&b) Yes these are both correct

    2) a&b) Whether you use isolation or not depends on what application you are using the AD4111 in, in particular if you are designing for EMC robustness. The primary application space for the AD4112 is Process Control Input Modules where this is very important due to operation in harsh EMI environments. Our evaluation board is based of an EMC board that is detailed in this App Note AN1572

    3) AVSS and DGND is our board do not use a star configuration. 

    Regards,

    Cathal.