SN74HC573A: The latched output failure

Such damage is typically caused by overvoltage or overcurrent.

Please show a schematic that shows what is connected to the output.

Is it possible for the output line to be touched by humans, or is it plugged/unplugged while in use?

If caused by EOS ,why the device sometime work well but sometime trouble? 

A NPN Transistor is connected to output pin to active a small coil of Electromagnet, the all of PCB be assembled in a shield case properly, so it's no way to be touched the output line by end user.

Please show a schematic.

Here attached schematic for your request.

Kindly advice ,tks.

Everything looks OK. I do not see any obvious way how the 573 could be affected.

It might be possible for switchign noise to be coupled into some other trace. Could you show an oscilloscope trace of an output and VCC while the coil is switched?

Attached photo (vcc and LE) combine with my previous attached photo (green color is output trace).

Plz have your further comment,tks.

Thanks your answer, I have informed the message to our R&D team to look into the detail, will update you later. 

Due to our system is negative control,the noise appear before vcc power on, but the output latch after LE 1mS pulse. looking into the signal after LE 1ms pulse is a pure ground wave,also Vcc are good without noise.We curious the relationship on before and after out trace because latch output pin transition is after the 1mS LE.

Please kindly more advice for us.

Thank you.

ivan wong said:

Due to our system is negative control,the noise appear before vcc power on, but the output latch after LE 1mS pulse. looking into the signal after LE 1ms pulse is a pure ground wave,also Vcc are good without noise.We curious the relationship on before and after out trace because latch output pin transition is after the 1mS LE.

I'm afraid I don't understand what you mean here.

Can you share a scope shot of the described operation?

Here no noise observe after power on. The mentioned noise in your last opinion cause by reference ground not yet provide that control by our system.

Please refer to attached I tried to explain that.

ivan wong said:

cause by reference ground not yet provide

Is there a time when the ground is floating in the system? This is a common cause of excessive current / damage to CMOS devices.

Switch the ground signal is our application .What reason affect to the defect device to output a non-completed wave (a lower level voltage 2~3v)? The fail rate is around 1/30 while repeat power on the system. Because replacement could solve the issue, what's variance between them?May you have a suggestion to improve it ? Thank you.

May you help us the information of contact window and shipping ,I am afraid there have no supplier could help me in Taiwan.

OK,I will try to find the support we got the parts from them.