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TM4C1231E6PZ GNDX PIN description changed in Nov. Y13 datasheet

Xiaowei Bai1
Intellectual 1205 points
Other Parts Discussed in Thread: TM4C1231E6PZ

Hi, 

My customer has reported they found the GNDX pin description has changed in Nov. Y13 TM4C1231E6PZ datasheet(There is a statement for this on page 32 of Nov. Y13 datasheet as below). It is a big bother to them. They have built the standard M4 board based on Apr. Y13 datasheet which the PIN is NOT connected to GND. But now, the most updated datasheet shows it should be connected to GND. Several answers are needed by them:

1, Why this PIN description is changed.

2, Which is recommended to them for future design.

3, For its mature product whose GNDX pin is NOT connected to GND. Do they need to change them all.

 

Detail information as below:

April 09, 2013 datasheet

November 15, 2013 datasheet

Anybody give me feedback for it? Thanks.

 

  • 0
    TI__Guru**** 244400 points

    Hi Xiaowei,

    The GND pin in Apr'13 datasheet and the digital GND in Nov'13 data sheet are the same ground reference. Recommendation is correct to connect it to Digital Ground.

    What has the customer connected to GNDX right now? Also is the Hibernate module being used by the customer?

    Amit

  • 0 in reply to Amit Ashara
    TI__Intellectual 1205 points

    Hi, Amit

    yes, customer's concern is GNDX connection, rather than GND.Customer have used TM4C1231E6PZ on their some products, and they have been MP at Aug'13. For these mature product whose GNDX pin is NOT connected to Digital Ground. but the describe it need connect to degital groud in Nov'13 datasheet, so do they need to change them all?

    For Also is the Hibernate module being used by the customer? yes.

    below is my question:

    1, Why this PIN description is changed?

    2, Which is recommended to them for future design?

    3, Do customer need to change old design all?

    thanks..

  • 0 in reply to Xiaowei Bai1
    TI__Guru**** 244400 points

    Hi Xiaowei,

    As I mentioned earlier, GND and digital ground is the same. You can refer to the System Design Guide

    http://www.ti.com/lit/an/spma059/spma059.pdf

    Section 3.7.1.2

    1. The Pin description has be re-worded.

    2. Recommendation is as per the System Design Guide

    3. What have they connected to GNDX to right now?

    Amit

  • 0 in reply to Amit Ashara
    TI__Intellectual 1205 points

    Amit

    3. What have they connected to GNDX to right now?

    Now, in customer design, GNDX without connected to digital ground. thanks..

  • 0 in reply to Xiaowei Bai1
    TI__Guru**** 244400 points

    Hello Xiaowei,

    So is the GNDX left floating?

    Amit

  • 0
    TI__Expert 3555 points

    Hi Xiaowei,

      If the customer has connected GNDX to the hibernate load capacitors only with no connection to digital ground as described in the April 9,2013 datasheet, they do not need to change their design.  It will function properly.  When wired like this, there is an opportunity for EMI noise to be coupled into the GNDX net if the system is operating in an environment with high EMI activity. 

      The November 15th datasheet change to make the connection of GNDX to and the hibernate load capacitors to digital ground was made to prevent possible EMI noise from being complied into the GNDX net.

     

    Regards,

    Ken

  • 0 in reply to Stellaris Ken
    Expert 1830 points

    Amit,

    With regard to the GNDX pin, you may want to consider the case for the TM4C129XNCAD microcontroller. As per TM4C1231E6PZ, the TM4C129XNCAD also recommends that GNDX not only be connected to the crystal, but also to digital ground. However, the TM4C129 Development Board, as seen in the User's Guide circuit diagram, does not connect GNDX to ground. It may make you feel more comfortable about the discrepancy knowing that although the datasheet states that GNDX should be connected to digital ground, at least in one TI implementation it was not.

    As Ken mentioned, there was a "change of heart" and connecting GNDX to digital ground does improve EMI immunity.

    Regards, Vito

  • 0 in reply to Vito Casa
    Guru 117855 points

    @ Vito,

    Superbly crafted/stated - mon ami.  Wish that same, "change of heart" - had earlier flowed to LM3S...

  • 0 in reply to Amit Ashara
    TI__Intellectual 1205 points

    Hi, Amit

    Yes, currently, GNDX is floating of customer's already MP product, thanks..

  • 0 in reply to Stellaris Ken
    TI__Intellectual 1205 points

    Hi, Ken

    Thanks for your reply, got it. I will communicate it with customer.

  • 0 in reply to Xiaowei Bai1
    TI__Guru**** 244400 points

    Hi Xiaowei

    As posted by Ken, a floating GNDX will make it more susceptible to EMI Noise in a system with EMI. The customer should take this into account.

    Amit