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AMC1301: Clearance Area below the chip

Eyal Bar
Prodigy 70 points

Part Number: AMC1301

Hi,

I'm using the AMC1301 in my project and i have a question about the clearance area.

According to the D.S, the area beneath the IC should be cleared of any conductive materials.

I have a multilayer board (14 layers), and i placed this IC on the top layer:

- Do I need to clear the area beneath the part in the top layer?

- In all the layer beneath it?

- Maybe 3 layers of clearance is enough?

Thank you for your answer,

Eyal Bar

  • 0
    Guru 140200 points

    Hi Eyal,

    due to possible bubbles, holes or other imperfections in the epoxy, even if they might be invisible, you cannot 100%-ly trust the isolation characteristics of epoxy. So, it's heavily recommended to clear the area in all layers!

    Kai

  • 0
    TI__Guru**** 183241 points
    Hi Eyal,

    To expand a little on Kai's response, it also depends on what voltage isolation levels you are trying to reach. Usually when high voltages are involved, there is a clear separation from the 'hot side' where the high voltage is to the 'low side' where all of the general user interface circuits live. It is usually not a good idea to route the low voltage circuits under the hot side since that could cause problems as Kai mentioned.
  • 0 in reply to Tom Hendrick
    Prodigy 70 points

    Hi,

    Thank you Tom and thanks to Kai.

    I'm trying to get to the bottom of this thing - the clearance is required to prevent a breach from the "high" voltage side to the "lower" voltage side?

    If that is the case, should i isolate the entire high voltage circuits and conductors?

    Thanks again,

    Eyal

  • 0 in reply to Eyal Bar
    TI__Guru**** 183241 points
    Hi Eyal,

    In a nutshell - Yes, that is correct. If this is a high voltage application, somewhere along the line you will need to do safety testing to verify the isolation voltage across the board, from the high voltage to the low voltage side. This is usually done with a HiPot tester, which measures the leakage currents while applying high voltage between various points on the board. If high and low voltage circuits are routed on top of each other, you can get arching through the material used to construct the PCB. There are high voltage materials available, but this adds significant cost to the board construction. It's easier to simply keep a clear separation through the PCB.