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UCD3138128: UCD3138128A and UCD3138128 Surge capability

Part Number: UCD3138128
Other Parts Discussed in Thread: , UCD3138

Hi Team,

My customer change the UCD3138128A to UCD3138128.

They see his board will reset when they test the surge CM2.0KV from system side through in.

and they try to turn the reset pin resistor value from R:220ohn to R:2.2Kohm and the reset situation is gone.

Could we have idea to know between A and nonA revision have different capability defense Surge ?

Or we have other comment about this issue cause his end customer just want to know what's different in both ?


  • The fact that actually increasing the resistor value prevents the reset suggests that there may be noise on the ground that the resistor is connected to.  We do not have specific surge data on things like the sensitivity of the reset pin to noise.  Noise sensitivity is a very complex issue, based on the totality of the circuit, including EMI, as well as the normal process variation of the chips.  

  • Hi Bower and Team,

    Thanks your comment.

    But cause your know , my customer just change the UCD chip can see this issue the other all of setting about his layout and any R/C value is keep the same.

    Why the nonA revision seems  weaker than A revision. Did you have any idea in here ? Because his end customer ask them to give some explanation. Thanks! 


  • Eddie, in general we see a bit more weakness in the A parts because they have some more logic, which produces more noise and draws more current.  There are so many possible set of noise factors, and, as I mentioned, there is normal production variation.  Has the customer followed the guidelines in the UCD3138 Practical Design Guideline Application Note?  It's here:  Following these guidelines is the best way to be safe from the noisy power supply environment.