"latch up"?

[cdcll]

after lightening, microcontroller did not work, and it is very hot, can not be reset, the only way to recover the system is power off and then turn on the power.

anybody can tell me how to solve this problem?

Thanks a lot!

 

[gloobox]

Hello,

can you describe a little bit your application?
what is the microcontroler, what kind of power supply?

you said "lightening", Is it a laboratory test to obtain an approval?
the first thing to do is to check the presence of voltage suppressor diodes, like SMBJor SMCJ for example (we use them for avionic systems), and to ensure that inputs or Psupply which are exposed to lightening are well filtered, thanks to a Pi ot T filter.

 

[cdcll]

gloobox, thank you!

the MCU is SM5964, using AC power supply, runing on the mountaintop. sometimes, after lightening, microcontroller does not work.

we also tested in the lab, 4KV at L-->ground, can obtain the approval.

what should I do to solve the problem?

Thanks!

 

[gloobox]

Hello,
Here are the protections we use in avionics systems.(28V supply)
The first picture shows protections used to clamp the lightening voltage.

The second picture shows the EMI filtering of the power supply.

if you ave a AC/DC converter powering your board, i suggest you to test these filters (between you Psupply and you board).
If they have no effect, try to shield your board, with a mecanical case, linked to earth ground: lightening involes high EMI fields which could explain the failures of your application.

@+

 

[cdcll]

Thanks!

Currently there are no filter & lightening protection circuit in our system, we use metal box, and have linked to the earth ground.

It seems that on the moutaintop, the grounding is not so good. because in the other place, the system works properly.

another problem I encountered is when we did the testing in the lab with surge from L to Ground(4KV), we found that the microcontroller sometimes was latch-up with the metal box, if we remove the metal box, the microcontroller can automatically reboot. Does it mean we need to do something with the mechanical side on the box?

anyway I will try your circuit first.

Thank you again for your help.