Hi,

I am making a GPS/GSM tracker based on the SIM808 chip plus a ATMega32u4.

The circuit is going to be installed in a car therefore it has to draw current from the noisy 12 volts in the car.
This is because of the alternator and various other components in the car, I have to isolate my sensitive RF circuit from the noisy 12V...

Which means protecting it from negative voltages, ESD discharges, and other high voltage discharges as seen in the picture below


Could someone give me advise on a good circuit for this application?

Thanks

 

I remember seeing a good thread on this topic here once. It's been a long time and I don't recall but try searching.

I did find this.
http://www.littelfuse.com/~/media/e...n_automotive_environment_application_note.pdf

 

You're going to be powering it from a 5V supply, more than likely a buck converter chip pcb, this is going to be the best choice for suppression, so looking at their datasheets is a good start.

 

You're going to be powering it from a 5V supply, more than likely a buck converter chip pcb, this is going to be the best choice for suppression, so looking at their datasheets is a good start.

Yeah, first im taking it trough a buck converter which converts it from 12V to 5V, then two LDO's that convert it from 5V to 3.3V and 4.1V.

But that buck converter wont survive those 300V peaks, at least not alone...

 

I remember seeing a good thread on this topic here once. It's been a long time and I don't recall but try searching.

I did find this.
http://www.littelfuse.com/~/media/e...n_automotive_environment_application_note.pdf

Yeah, ive also seen that one,

It explains the problem, but doesnt provide any circuit to eliminate these spikes...

 

Yeah, ive also seen that one,

It explains the problem, but doesnt provide any circuit to eliminate these spikes...

I think the thread I remember linked to (or attached) an old article about dealing with automotive systems. Maybe it was even authored by the infamous Bob Pease, but I don't recall.

 

Yeah, first im taking it trough a buck converter which converts it from 12V to 5V, then two LDO's that convert it from 5V to 3.3V and 4.1V.

But that buck converter wont survive those 300V peaks, at least not alone...

Then you're going to need Mov's or Tvs dodes on the battery supply.