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ISO7231(isolator) 1 Layer PCB guideline?

Jin-Suk Choi
Intellectual 2270 points

Hi~

In ISO7231 datasheet, it suggest to use 4 layer PCB for proper communication, but customer want to use 1 layer PCB.

Is there any guideline or special point for 1 layer isolator design?

Thanks.

  • 0
    TI__Intellectual 2270 points
    One more, is there need any special SMD profile for ISO7231? Customer has 235deg SMD reflow profile(max 260deg), so want to check if SMD max temperature is reaches up to 260deg is okay or not.
  • 0 in reply to Jin-Suk Choi
    TI__Guru 55795 points
    Hi Jin,

    Could you please tell me more about ISO7231 design? What is the datarate customer is running the device at?
    If the datarate is less than 100kbps and there aren't many components on the PCB for routing, one Layer PCB can still be used by following rest of Layout Guidelines in Section 12 of datasheet. Few other points to note,
    1. EN strongly pulled HIGH.
    2. Decaps (0.1µF) placed as close as possible to device VCC & GND pins.

    Regarding Reflow Temperature profile of ISO7231, a max of 260C is supported in reflow profile.

    Regards,
    Koteshwar Rao
  • 0 in reply to Jin-Suk Choi
    TI__Intellectual 2200 points

    Hi Jin-Suk,

    We have not done any testing on ISO723x with a 1 layer PCB.  I think this maybe ok for low data-rates (<10Mbps) but may be difficult for higher data-rates. I would suggest including 100 Ohm resistors in the path of the output buffers to slow down the rise/fall times. Similarly, the devices driving the ISO723x should have slow rise fall times. Also place the bypass capacitor on VCC1 and VCC2, between pins 1 and 2, and between pins 15 and 16 respectively.

    Regarding the reflow temperature, upto 260 C is supported. 

    This is described in the Addendum-Page 1 under MSL Peak Temp: "Level-3-260C-168 HR"

    Rgds,

    Anant