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external pull-up for MSP430F5237

Jason Kang
Intellectual 470 points

Other Parts Discussed in Thread: MSP430F5237

Hi. 

In my current circuit-design, I2S signals from MSP430F5237 have pull-up to 3.3V power.

According to the description in “SLAA558-Nov 2012 (page 2)”, I am advised to connect the pull-up to DVIO instead of DVCC as shown below.

************************************** note ********************************

NOTE: In split supply I/O systems, if external pullup resistors are connected to any of the DVIO
supplied pins (for example, the USCI I2C pins – SDA and SCL), tie the external pullups to
the DVIO supply and not to DVCC.

********************************** ******************************************

By the way, DVIO is not available in MSP430F5237. Therefore, pulling-up I2C to DVIO is not possible.  

So, should I route I2S signals without placing external pull-up's because there are already internal pull-ups? In other words, should I remove the external pull-ups (to 3.3V)? 

Thank you. 

  • 0
    TI__Mastermind 22985 points

    Jason,

    First off, I am assuming you are using the I2C module in the USCI to drive your I2S signals, correcT?

    The app note you reference applies to F522x and F521x parts that have a separate DVIO rail (to allow some IOs to run at a different voltage than Vcc, e.g Vcc = 3.3V, VIO = 1.8V).  The F523x part you are using does not have the separate DVIO rail, and all IOs run at Vcc.  Therefore it is correct to use external pullups to Vcc.  Typically the internal pullups on the 430 IOs are too weak to be useful for I2C operation at any reasonable speeds.

    Mike

  • 0 in reply to Mike Pridgen
    Intellectual 470 points

    Thank you. 

    It is so clear. 

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