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TIC12400-Q1: schematic question

Arie Li
Expert 3390 points

Part Number: TIC12400-Q1

Hi experts,

My customer is doing schematic design with TIC12400-Q1. I have two questions to doule check with you. Thank you.

1. Is it OK to connect AGND and DGND directly? I found both datasheed and EVM schematic is doing in this way.

2. Can customer add resistors at INx pin? Currenly they add 220ohms at each pin, is it OK to do that?

  • 0
    TI__Guru 74872 points

    Arie,

    1. Yes this is okay. If you only have one GND in your system, this is how it should be connected. 

    2. Are the resistors in series with a switch or another component? Are they pulled to GND? Either way should be okay, I'm just curious.

    Regards,

    Eric Hackett 

  • 0
    TI__Mastermind 36741 points

    Hi Arie,

    As Eric has said, a single ground is fine.  Sometimes the grounds are split apart to help isolate the digital signals that are local to the board and MCU from possible noise coupling into the system on one of the analog input cables which have switches that are external to the board.  In the layout you may want to make sure the digital and analog input traces are routed apart from each other to avoid coupling noise through the shared ground plane.

    Series resistors are not just OK, they are preferred.  They help to limit current in the event of a fault condition or ESD event.  It's often common to add a capacitor to GND on each input pin as well.  See the TIC12400-Q1 and TIC10024-Q1 ISO-10605 ESD Test Report for additional information.

    Regards,

    Jonathan