what is ADM3053's reference power layer in 4-layer PCB design?

Hi Caroline,

   I'd encourage you to follow the PCB layout and layer assignments as used in the ADM3053's evaluation board EVAL-ADM3053EBZ, at least in the area surrounding the ADM3053. The different layers are shown in the eval board's user guide.  This board was tested and passed EN55022 Class B for radiated emissions. 

  In terms of your question about the connection between pins 12 & 19, these pins should be connected through a ferrite bead and using a wide trace (not plane) between the ferrite and Pin 19.  See the PCB Layout Recommendations section on page 4 of the user guide.

Eric

ps  Some resources which discuss the considerations behind the design choices in the evaluation board are AN-0971 Recommendations for Control of Radiated Emissions with isoPower Devices or AN-1349 PCB Implementation Guidelines to Minimize Radiated Emissions on the ADM2582E/ADM2587E RS-485/RS-422 Transceivers.  Note that AN-1349 is specifically for a different part, but the concepts and guidelines are similar.

Hi Caroline,

   I'd encourage you to follow the PCB layout and layer assignments as used in the ADM3053's evaluation board EVAL-ADM3053EBZ, at least in the area surrounding the ADM3053. The different layers are shown in the eval board's user guide.  This board was tested and passed EN55022 Class B for radiated emissions. 

  In terms of your question about the connection between pins 12 & 19, these pins should be connected through a ferrite bead and using a wide trace (not plane) between the ferrite and Pin 19.  See the PCB Layout Recommendations section on page 4 of the user guide.

Eric

ps  Some resources which discuss the considerations behind the design choices in the evaluation board are AN-0971 Recommendations for Control of Radiated Emissions with isoPower Devices or AN-1349 PCB Implementation Guidelines to Minimize Radiated Emissions on the ADM2582E/ADM2587E RS-485/RS-422 Transceivers.  Note that AN-1349 is specifically for a different part, but the concepts and guidelines are similar.