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Original question:

MSP430F5659 PUR pin

MSP430F5528: Resistors for USB PUR line on MSP430's

Kuenrg
Intellectual 480 points

Part Number: MSP430F5528
Other Parts Discussed in Thread: MSP430F5529

I'm doing a review and noticed that the majority of designs (including the MSP430F5529 Launchpad - http://www.ti.com/lit/ug/slau533d/slau533d.pdf) have the PUR line connected to DP via a 1.4k resistor and _then_ the DP line is pulled to ground with a 1M resistor.

This is in contrast to what I understand from the data sheet and this post https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/409722

where PUR should be pulled directly to GND via 1M AND also connected to DP via a 1.4k.

ie should the 1.4k and 1M resistors have a common point on the PUR pin or on the DP line?

(I'm pretty sure that due to the great difference between the values that both configurations actually work - I just want to know what the "correct" configuration is.)

Thanks

  • 0
    TI__Mastermind 40195 points

    Hi,

    See from the targetboard. It is same as our launchpad.

    What do you mean "what I understand from the data sheet"? Here? actually PUR is pulled to ground with a about 1M resistor. I advice you to follow our target board schematic, which has been proved for a long time.

    Eason

  • 0 in reply to Eason Zhou
    Intellectual 480 points

    Thanks for the reply - I'll try to clarify:

    This is how the launchpad and target dev board are done:

    Below is how I read it should be implemented based on Section 6.5.1 of the datasheet and the recommendations on e2e. Note how the top connection of R15 has changed. Since R16 is three orders of magnitude smaller than R15 I understand that it really shouldn’t make a difference.

    As you mentioned, we're are leaving it the way the Launchpad is done because it is tested but during my schematic review I came across this difference.
    Thanks

  • 0 in reply to Kuenrg
    TI__Mastermind 40195 points

    I know what you mean, sorry for my English. As I know for 1M resistor, it will has about 1% error, so we can overlook the 1.4K resistor. But this is based on the resistor between MSP430 pin is maxmum. Actually it is not. From an official level, I will advice you to follow the launchpad. From my personal view, it is fine. Thank you for your clarify.

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