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SN74LVC1G123: Output failure

Nicolas Chiappinelli
Prodigy 10 points

Part Number: SN74LVC1G123

Hello,

I've detected a failure on one cirucit that use the SN74LVC1G123.

The circuit is the one below:

Screenshot 2026-01-02 155626.png

Apparently the timing circuit short the capacitor but don't start the charging phase.

Because the system is a medical device such failure can't be accepted.

In the first images (the working circuit) below on the second trace there is Vc. The behaviour is as described in the datasheet. After a trigger event, the capacitor is shorted and then the charging phase starts. In the second image (the failed circuit) Vc after an initial short can't start to rise.

Vc - working circuit.jpgVc - Failed circuit.jpg

  • 0
    TI__Genius 10910 points

    Hi Nicolas,

    I don't see any problem with the schematic.

    The oscilloscope images show CH2 is the voltage across C23, correct? What is CH1?

    Regards,

    Nikki

  • 0 in reply to Nikki Dengel
    Prodigy 10 points

    Hi Nikki,

    yes, you are right. the channel 1 is the input B.

    Regards,

    Nicolas

  • 0 in reply to Nicolas Chiappinelli
    TI__Genius 10910 points

    Hi Nicolas,

    I can't find the source of the problem based on the oscilloscope shots and schematic. The schematic seems fine, and the oscilloscope clearly shows abnormal behavior. Some possibilities include ESD damage or physical damage to the device, but it's hard for me to say with the information I have.

    If you would like, I am happy to continue with the debug process with you online, but I recommend starting the return process with your supplier. The page Customer Returns describes the process.

    If you suspect user error, I can try to help. I'd be interested in whether this problem has occurred with several devices or just one. And has this problem occurred after working without issue for a long time? ESD damage or physical damage are also other possibilities that we can diagnose during the return process. However, it's up to you whether you'd like to continue this process online or if you'd like to start a return. Let me know what you decide.

    Regards,

    Nikki