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UCC2818A: Is there any state

Kazuya Nakai59
Guru 21515 points
Part Number: UCC2818A

Tool/software:

Hello guys,

One of my customers use UCC2818A for their mass-production.

They found a phenomenon where the SS voltage does not rise above 1V.
We know I know that this occurs when the capacitor between SS and GND has leak current.
But the capacitor does not have any leak current.

At this moment, they have the following question.
Could you please give me your reply.

Q.
Does UCC2818A has any mode which occurs this phenomenon?

Your reply would be much appreciated.

Best regards,
Kazuya.
 

  • 0
    TI__Mastermind 40120 points

    Hello Kazuya-san, 

    There is no known internal state or operating mode or circuit that limits the SS voltage to 1V. 

    Since your customer is in mass-production and they "found" this phenomenon, I presume that the occurrence is a small percentage of the total build. 
    My presumption is not to minimize or dismiss the concern, but to establish a basis for my hypothesis. 

    I agree that a leaky capacitor could account for the pull-down to 1V.  Assuming that the cap has been removed and checked out or replaced and the 1V level is not corrected, I conclude that the SS input must have become damaged somehow.  I also assume that there is no external circuitry (other than the SS cap) connected to the pin.
    Given these assumptions, my first inclination is to suspect ESD damage.   

    ESD might be unknowingly applied to the board (and SS pin) during board handling and/or board test.  Some small percentage of the boards may become damaged from random or systematic ESD strikes which exceed the device rating (per datasheet: +/-2000V HBM, +/-1500V CDM). 

    My assumptions may be wrong, and some other reason can account for the problem, but without additional information on this application, ESD is the most likely cause that I can think of.  

    Regards,
    Ulrich