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UCD3138: Connection of AGND and DGND

Part Number: UCD3138

There is a problem with the UCD3138 and we are investigating the cause.

 

As a prerequisite, I understand that the 9.1 Layout Guidelines in the data sheet and the reference manual (SLUSAP2I) recommend a single GND pattern layout.

 

If you do not follow the recommended single GND, please let me know if the following events can occur.

 

The noise between GND was over 0.3V as attached. If a reset occurs at this time, but if the Ground difference deviates from 0.3V, will it cause a reset?

(It has been confirmed by waveform that V33D is not lower than VGL and /RESET pin is not lower than 2.5V when a reset occurs.)

 

In addition, as a countermeasure against the reset event, when the GND structure that was not recommended (the GND was separated) was changed to Single Ground, the reset event no longer occurred. I want to confirm the effectiveness of the measures.

  • We recommend following the Practical Design Guidelines document here:

    https://www.ti.com/lit/an/slua779b/slua779b.pdf

    Not following these guidelines can certainly lead to issues with reset.  

    Like other microcontroller manufacturers, we provide design guidelines rather than power supply rejection information.  

    Power supply rejection doesn't really apply to digital circuits very well.  

    Certainly power supply differences like you describe could cause a reset.