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MSP430F5329: 1MΩ pull-down resistor on pin 63

Yamen Alimam
Prodigy 20 points
Part Number: MSP430F5329
Other Parts Discussed in Thread: MSP430F5529,

Hello,

It is recommended to connect a 1MΩ resistor to ground on pin 63 (PUR) of the MSP430F5529 if the USB interface is not used. Can this resistor also be placed on the same pin of the MSP430F5329 without impacting performance or functionality? The MSP430F5329 lists this pin as NC, but we would prefer a single layout for both microcontrollers.

Thanks

  • 0
    TI__Intellectual 1940 points

    Hi Yamen, 

    Is there any reason you can just not populate the resistor there? you may get tiny leakage here, and without knowing the rest of the surrounding components this may or may not cause an issue. Even though I'm sure it will be very tiny. 

    Typically its safer to just leave the NC pin unconnected. So a slight change in the BOM of your system by not populating the 1M resistor. 

    In reality, it shouldn't be an issue but in some extreme rare cases it seems like it can be a possibility. I think you are fine to do your original plan. 

    regards, 

    Henok

  • 0 in reply to Henok Taffere
    Prodigy 20 points

    Hi Henok,

    We would require two BOMS by selectively not populating the resistor, which we are also trying to avoid.

    So our only concern by placing the resistor on the NC pin is a tiny leakage current.

    What is the voltage level on the NC pin during a given operation? For example, given a supply voltage of 3.3V, should I assume the leakage current will fluctuate because the pin is floating or will it always be 3.3 µA (3.3V / 1MΩ)?

    Thanks

  • 0 in reply to Yamen Alimam
    TI__Guru 63021 points

    Hi Yamen,

    Let me confirm with design team if resistor is required.

  • 0 in reply to Dennis Lehman
    Prodigy 20 points

    Hi Dennis,

    Just to clarify, our plan is to populate the resistor for both microcontrollers, regardless of if it is required. We just want to ensure there are no adverse effects to connecting the resistor to the NC pin of the MSP430F5329.

    Thanks

  • 0 in reply to Yamen Alimam
    TI__Intellectual 1940 points

    Yamen, 

    I am currently out of office and will return to the Tuesday. I should have a response from the design team by then. 

    Will update you. 

    regards, 

    Henok

  • 0 in reply to Yamen Alimam
    TI__Intellectual 1940 points

    Yamen, 

    Sorry for the delay. There are some communication issues, as it seems my point of contact is out of office. 

    Will get back to you when I can, soon hopefully. 

    regards, 

    Henok

  • 0 in reply to Yamen Alimam
    TI__Intellectual 1940 points

    Yamen, 

    I just received confirmation that you are good to go with your original plan, you can expect for the resistor to have no effect. 

    The USB circuit diagram in section 9.10.13 Port PU in the F5529 datasheet shows this. You would need to manually configure the PU pins (PUSEL, PUREN) in 5529 but in F5329 they stay in default state where no current is being sourced. 

    regards, 

    Henok

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