pmod 410-310 isolated ground and VSION

[PurplePig]

What is the source of the VISOIN on the board - It does not show a connection on the 500-310 schematic

I see ISOground sits on J1. Can/Should I ground that to an external receiver?

 

Does this need to be connected to the destination hardware. I am seeing an odd shift in voltage when connecting the board to a Microgate Synclink (https://microgate.com/#/USBAdapter/)

 

See the attached o-scope images for Microgate attached and unattached

 

With Microgate connected

With Output disconnected

[JColvin]

Hi @PurplePig,

The design engineer does really remember anything about this product that they designed nearly 10 years ago, so the following information is going to be my best educated guess after reading through the ADM2582E datasheet from Analog Devices (https://www.analog.com/media/en/technical-documentation/data-sheets/ADM2582E_2587E.pdf) and some of the referenced Application Notes from that datasheet.

VISOIN is sourced from VISOUT via a PCB trace; VISOUT comes from a "isoPower integrated dc-to-dc converter" as per the Applications Information section of the above datasheet. From the best that I can tell, this isolated voltage doesn't actually get used anywhere or at least the two Evaluation boards that are referenced in the datasheet, https://www.analog.com/media/en/technical-documentation/user-guides/EVAL-ADM2582EEMIZ-2587EEMIZ-UG-916.pdf?doc=ADM2582E_2587E.pdf and https://www.analog.com/media/en/technical-documentation/user-guides/UG-044.pdf?doc=ADM2582E_2587E.pdf, do not load the resistors to connect the VISO voltage to any of the outputs as per their schematic and bill of materials.

I am less certain about the ISOGND (GND2 as labeled in the ADI datasheet). There is a contact point present on the two ADI evaluation boards, but I'm not finding anything definitive of if this should or should not be connected to the network, but that might be because I didn't read the multiple application notes carefully enough. I did see that the evaluation boards have a pad for an unloaded resistor RT since that resistor "must be removed if the board is connected to a bus that is already terminated at both ends".

It's also worth noting that the datasheet for the ADM2582E specifically recommends having ferrite beads between some of the GND2 connections which the Pmod RS485 does not have. I do not know what the implications are aside from potentially not passing the EN55022 radiated emissions standard.

Thanks,
JColvin