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AM3352 RTC Question

Ignacio Linares
Expert 1655 points
Other Parts Discussed in Thread: AM3352

My customer has the following questions:

I have a question on depopulating the RTC crystal on the AM3352 

According to the AM335x Schematic Checklist 

If RTC internal oscillator is not used... 

This can be the case when: 

A 1.8 volt LVCMOS clock source is used rather than a crystal circuit

Connect the clock source to the RTC_XTALIN terminal, leave the RTC_XTALOUT terminal open-circuit, and connect VSS_RTC to VSS if using the ZCZ package option 

The AM335x RTC is not used

Leave the RTC_XTALIN and RTC_XTALOUT terminals open-circuit, and connect VSS_RTC to VSS if using the ZCZ package option 

Is there a typo in “connect VSS_RTC to VSS” because it already is, both are ground connections.

 

  1. Does the VDDS_RTC pin need to be connected to VSS_RTC and VSS?
  2. Or does power need to be kept on the VDDS_RTC pin?
  3. Or does the VDDS_RTC pin need to be left floating?

Pic.docx

  • 0
    TI__Guru 62855 points

    The original plan was to use VSS_RTC as a Kelvin ground connection when using a crystal.  However, using VSS_RTC as a Kelvin ground caused unexpected noise issues.  See Advisory 1.0.30 for more information.

    This is why the data sheet tells you to connect VSS_RTC to VSS.

    VDDS_RTC should be connected to a 1.8 volt power source.

    Regards,
    Paul