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TCA9617A: length limit

[FAE] Andrew Wang
Genius 10685 points
Part Number: TCA9617A

Hi Team,

Customer wants to know this device output length limit, a rough number is also fine, thanks.

Andrew

  • 0
    TI__Guru 72711 points

    Hey Andrew,

    The answer for this depends on if you are working at fast mode plus (1 MHz) or fast mode (400 kHz). The max capacitance allowed for fast mode plus is 550pF while fast mode allows 400pF.

    You can use the Saturn PCB tool to estimate trace capacitance here:

    From the image above, a 5mil width and a 10 mill height with a copper weight of 1 oz and plating thickness of 1oz gives us about 1.7pF per inch.

    fast mode = 400pF/1.7pF/inch = 235 inches

    fast mode plus = 550pF/1.7pF/inch = 323 inches

    ----------------------------------

    If I changed the width to 14mils then parasitic capacitance then goes to 2.73pF/inch

    fast mode = 400pF/2.73pF/inch = 146 inches

    fast mode plus = 550pF/1.7pF/inch = 201 inches

    You can play around with this yourself if you download the tool.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    TI__Intellectual 2600 points

    Hi Bobby,

    I have a further question regarding this tool,

    for the frequency here, shouldn't I change to 1MHz(fast mode plus) or 400Hz(fast mode)?

    for the option here , I should check with customer about the PCB material(Copper weight, plating thickness,Er) they use and change the

    options to get trace capacitance ,right?

     big thanks for your answer in advance!

    -Andy

  • 0 in reply to Andy_Lin
    TI__Guru 72711 points

    Hey Andy,

    "for the frequency here, shouldn't I change to 1MHz(fast mode plus) or 400Hz(fast mode)?"

    You can if you'd like. I played around with this a little and did not find much change when messing with the frequency.

    "I should check with customer about the PCB material(Copper weight, plating thickness,Er) they use and change the

    options to get trace capacitance ,right?"

    Yes, this will get you a more accurate estimation.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    TI__Intellectual 2600 points
    Thanks Bobby!
    so many thanks for your suggestion!

    -Andy