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TMS570LS1227: How to configure unused pins

SY Yoon
Genius 3381 points
Part Number: TMS570LS1227

Hi,

How do I configure unused pins?

There are no information in the datasheet and the TRM.

I found only comment as below in the datasheet.

Internal pullup/pulldown allows unused I/O pins to be left unconnected

If unused pins are unconnected, how should I set the internal resistance?

  • 0
    TI__Guru**** 197036 points

    Hi SY,

    To provide a balance between flexibility and EMI reduction on the design, you can leave the unused pin unconnected, set it as an input with internal or external pullup or pulldown. leave the input pin floating makes it a perfect magnet for attracting ESD or EMI.

    For output only pin, it’s a good practice to connect it to an external pullup/pulldown resistor.

  • 0 in reply to QJ Wang
    Genius 3381 points

    Hi, QJ

    I have a question in your answer.

    For output only pin, it’s a good practice to connect it to an external pullup/pulldown resistor.

    Which is better, pullup or pulldown?

  • 0 in reply to SY Yoon
    TI__Guru**** 197036 points

    Hi SY,

    For PGE package, actually you can leave the unused output only pin as floating to save PCB space and BOM cost. 

    For ZWT package, I'd like to add pull (up or down) to an unused pin because I may use this pin during testing or debugging.