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TMS570LC4357-SEP: Clarification on Pin Termination

Dhir Gandhi
Prodigy 210 points
Part Number: TMS570LC4357-SEP


Tool/software:

Hello,

I was reviewing the TMS570LC4357-SEP TID Radiation Report and had a question regarding the termination used for the pins. I’d like to understand how it was determined whether to apply a pull-up or pull-down resistor to a pin.

For example, in the case of pins R12 and R13 — both are outputs by default, yet one is pulled up while the other is pulled down. Understanding this rationale will help me decide how to terminate unused pins on my custom board using this MCU.

 

  • 0
    TI__Guru 74031 points

    Hi Dhir Gandhi,

    Apologies for the delayed response!

    While specific radiation testing information for pins R12 and R13 isn't directly available in the searched documentation, general practices for radiation-hardened designs suggest:

    • Using defined logic levels rather than floating states
    • Implementing appropriate pull-up or pull-down resistors to maintain known states during potential radiation events
    • Considering the fail-safe state of the pin in case of radiation-induced effects
    Unused Pin Recommendations: For unused pins on your custom board, you should:
    • Follow the device-specific recommendations in the datasheet for unused pin termination
    • Consider the radiation environment and implement appropriate pull-up or pull-down resistors based on the desired fail-safe state
    • Ensure pins are not left floating, which could lead to undefined states during radiation events

    --
    Thanks & regards,
    Jagadish.

  • 0 in reply to jagadish gundavarapu
    Prodigy 210 points

    Hello Jagadish,
    Thank you for your response. However, I would like to request that you please review my query once again, as the suggestion provided does not address my concern.

    jagadish gundavarapu said:
    • Follow the device-specific recommendations in the datasheet for unused pin termination

    Additionally, I was unable to find any recommendations regarding pin termination in the datasheet.

    Lastly, I kindly ask that AI tools not be used to generate responses. I am posting on E2E to receive a well-considered and helpful answer, even if it takes some additional time.

  • 0 in reply to Dhir Gandhi
    TI__Guru 74031 points

    Hi Dhir,

    Apologies for the delayed response.

    You are right, i used our internal TI tool, the advantage of this tool is fed with all our e2e data base along with all the manuals. And after generating its response i verified and found that it is meaningful and correct. That is the reason i shared to you.

    Currently there is no active development going on with this device and very limited support is available. If needed i will try to check with internal team to get a response on it, it might take some delay.

    --
    Thanks & regards,
    Jagadish.

  • 0 in reply to jagadish gundavarapu
    Prodigy 210 points

    Hello Jagadish,
    Thanks for the revert.

    jagadish gundavarapu said:
    i used our internal TI tool, the advantage of this tool is fed with all our e2e data base along with all the manuals. And after generating its response i verified and found that it is meaningful and correct. That is the reason i shared to you.

    Okay, but still I am not able to find any pin termination recommendations in the datasheet. Kindly help me with the same.

    jagadish gundavarapu said:
    If needed i will try to check with internal team to get a response on it, it might take some delay.

    Please check with internal team.

  • 0 in reply to Dhir Gandhi
    TI__Expert 5800 points

    Dhir,

    I have reviewed this thread and other information on this device.

    The resistors pull up/down in the test report were arbitrarily chosen.  Generally, they alternate pull up and down, except when functionality dictated otherwise.  This test board is not intended to be used as a reference design for application implementation.  I would recommend the same suggestions as Jagadish did at first, to choose pulls according to the application need.  Generally, for output buffers, no pull is required since the device is driving the pin.  Only include them if you need to ensure the signal is always driven, even when the device output buffer is not active.  

    Best regards,

    Jason