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TLIN1029-Q1: 220pF at LIN pin in simplified schematics of datasheet

Masatoshi Oguri
Expert 4780 points
Part Number: TLIN1029-Q1


Hello,

There is a 220pF at LIN pin in the simplified schematics. It looks like parasitic capacitance of the cable. But in Layout Guidelines of the datasheet it is "For slave applications a 220 pF capacitor to ground is implemented.". Who does implement it and where and how is it implemented?

Where did 220pF come from instead of 200pF?

Thanks.

Regards,

Oguri (TIJ automotive FAE)

  • 0
    TI__Expert 4780 points

    I made a wrong post. I found the 220pF a discreet part in Figure 33 as 1 of 2 C3.

    I would like to know why you changed it from 200pF to 220pF.

    Thanks!

    Oguri

  • 0 in reply to Masatoshi Oguri
    TI__Guru 62920 points

    Hello Oguri-san,

    I can explain the situation.  You are correct that this capacitance is external to the device.  220 pF is a common value used in many end applications and in some compliance testing.  It was the original value given in the typical application schematics in the datasheet, but at that time the datasheet also specified a maximum capacitance of the LIN pin as 45 pF.  The LIN standard recommends slave node capacitance be no higher than 250 pF, and the combination of 220 pF external capacitance and 45 pF internal capacitance exceeded this.  Initially the solution to this discrepancy was reduce the recommended external capacitance to 200 pF.  (This change was made in Revision C, published July 2019.)

    However, we also revisited the characterization of this parameter.  In this investigation we found that it was originally specified higher than needed and that a 25 pF maximum specification could be supported.  This was a better solution since it allowed for compatibility with existing designs using the common 220 pF external value.  After this determination we reverted the Rev. C changes to the external recommended value and reduced the CLINPIN specification from 45 pF maximum to 25 pF maximum in Rev. D (published March 2020).

    Please let me know if that is not clear or if you have further questions.

    Regards,
    Max Robertson