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ISO224: PCB Layout inquiry

Ryan Sadler
Prodigy 10 points
Part Number: ISO224

I am currently working a PCB layout using the ISO224BDWVR isolation amplifiers.  I am looking at the recommended layout example on the datasheet (section 11.2) particularly the clearance area that is to be kept free of any conductive materials; looking for more info on the rationale for this clearance area, as I would like to consider placing a second ISO224 part on the opposite side of the board as the first ISO224 part, where both parts use the same clearance area.  Board thickness would be ~3mm.  Curious if this clearance area is for sake of isolation integrity or more for RE concerns out of the part and if "stacking" two parts could potentially cause interference amongst each other.

  • 0
    TI__Guru**** 180931 points

    Hi Ryan,

    The footprint of the ISO224 provides ~9mm of clearance from the high voltage side to the user side - any tracking that is included under the "clearance area that is to be kept free of any conductive materials" will reduce the maximum clearance that the package provides.  In the end, it depends on what level of clearance your product needs.  If it's less than 9mm, your could run traces under the ISO224.  Putting two devices mirror imaged on the top and bottom layer should not be an issue as long as both 'high side' circuits are at the same potential.  If they are not, then your safety inspector may question the 3mm distance through your PCB from one hot circuit to the other.  Assuming you are using FR4, there is an advantage to routing two different HV circuits on opposite sides of the PCB, but aging effects of the FR4 material can reduce the isolation capacity over time.  You will need to sort that out with your certification team depending on the end use of the equipment.