SN74LV06A: Abnormal Output level

Hi Kengo,

I've never seen a failure like this.

Kengo.Y said:

This is measured only with the IC.

It looks like the output is driving high - is there not a resistor pulling up the line?

Is this just one device or have you seen the same type of failure on more than one?

How long was the output low before this scope shot was taken? Also, does it ever recover from the state where it will not go low?

Hi Emrys,

thank you for your reply.
Bellow is a test circuite.

Emrys Maier said:

Is this just one device or have you seen the same type of failure on more than one?

  -> Just one device and only 1Y port.

Emrys Maier said:

How long was the output low before this scope shot was taken? Also, does it ever recover from the state where it will not go low?

  -> This phenomenon rarely occurs.

Sincerely.
Kengo.

Hi Kengo,

Kengo.Y said:

This phenomenon rarely occurs.

This doesn't answer either of my questions -- was your scope shot taken just at random, or did you know this would happen? How did you know when to trigger?  Is this a repeatable issue?

Looking at the scope shot provided,

It looks like the output driver is already very weak (VOL should be under 0.25V with this load) probably due to some form of damage, but then it gets weaker until it can no longer drive the output at all. I marked the current into the output at each level based on the shown resistor value (620 ohms).

I find this most odd since it remains constant at the start, but changes after each time the transistor is shut off. At the end it doesn't seem to start recovery at all when the input is held high -- but this is also a relatively short timeframe. Perhaps with a longer time the output would recover.

Hi Emrys,

Thank you for your comment.

Is the SN74LV06A have an ESD diode at output?
If Yes, I suspect that this ESD diode may be broken.

Sincerely.
Kengo.

Yes, there is an ESD diode on all pins of the device -- I've never seen an ESD diode do what you've shown. Why would you think that?