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UCD90160: analog and digital grounds

Binayak Shrestha88
Expert 1520 points
Part Number: UCD90160
Other Parts Discussed in Thread: ADC16V130

Hi,

I am using the power sequencer UCD90160 in my design. It has 3 analog ground pins (AVSS3, AVSS2, AVSS31) for the 16-bit ADC inside. The userguide mentions them as analog ground pins. This chip also has three digital ground pins (DVSS3, DVSS2, DVSS31).

From my experience, I have an understanding that these pins are named analog ground and digital ground due to the existence of separate physical grounds inside the IC. On the PCB board, they should be tied together to one single ground plane.  Am I correct on this? I think the same has been told by TI employee while explaining the grounding required for one of the ADCs (ADC16V130).

I am sharing the url of that post:

e2e.ti.com/.../1565632

In my board, all signal layers have tightly coupled  continuous ground planes adjacent to them so that the signals and their return paths are clearly defined. I don't want to cut the ground plane (to create analog ground) and invite hordes of problems like unanticipated return path loops, potential EMI creation, etc.

Will I be correct to connect all the digital ground pins and analog ground pins to a single ground plane?

 

Warm Regards,

Binayak.

 

 

 

  • 0
    TI__Genius 9845 points
    You are correct, Binayak. AVSS and DVSS refers to the internal circuit that these ground pins are connected to. Outside the package, they can connect to one common solid ground. But this ground is better to be a "quiet" ground, otherwise noise will be introduced to ADC results.
  • 0 in reply to Zhiyuan Hu
    Expert 1520 points

    Hi Zhiyuan,

    Thanks for the reply.

    I believe it will all depend on how I will route my signals. If my high switching digital signals don't share return path with sensitive analog signals, I don't think I need to worry too much. In other words, things should be fine if the field space of analog signals and digital signals are separate.

    Normally an ADC would have sensitive analog signals as inputs. However, in the case of a sequencer, the signals that we are monitoring (as inputs to the ADC) are the power rails. These power rails provide power to core and I/Os of different devices like DSPs and FPGAs which switch at very high frequencies. So where are sensitive analog signals in case of the power sequencer?

    Warm Regards,

    Binayak.

  • 0 in reply to Binayak Shrestha88
    TI__Genius 9845 points
    For sequencing, there is no critical signal. You can add filtering caps from MON pin to to ground to remove possible noise. The ground potential difference between the UCD and the regulation point of the rail voltage may introduce some measurement error. But it is not critical for sequencing purpose.