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ISOW1412: RS485 resistors clarification

Part Number: ISOW1412
Other Parts Discussed in Thread: ISO1410

Hello everyone,

 

Our customer is using the ISOW1412 RS-485/RS-422 transceiver. On their PCB they placed three 49.9K ohm resistors (R221, R22, R223) and one selectable 121-ohm resistor (R224) as shown the attached f1 image.

On the ISOW1412 datasheet we didn’t found information about the previously mentioned resistors, as per our understanding R221 and R223 are needed by the typical RS485 transceivers and when consulting the documentation of the ISO1410 (which is a similar part number), we noted that such IC does not need those as shown the attached f2 image.

Could you please confirm if the ISOW1412 RS-485/RS-422 transceiver needs the R221, R22, R223 resistors that our customer placed?

 /cfs-file/__key/communityserver-discussions-components-files/1013/images.zip

Any guidance will be appreciated,

Best regards,

Esteban V.