Hello,

Kai, in a previous post I said that the environmental constraints are defined by the standards used. I told that in my case this was truck application. You should consider that trucks have some huge differences with cars. There is some electromagnetic parts as retarders that can makes some incredibles pulses. Also, the lengh of wires between two ECU could be more than 30 meters. I hope it's less in a car...
I've also worked for a car constructor and the electrical constraints defined by standards were below that I've seen in trucks constructors...

When you're saying you've put a fuse and transzorb and so on, I hope you've designed it to be compliant with the standard used in car application. Otherwise, you should expect some problems in future. Even if your protection seems to work, do no forget that some events may generate some disturbances impossible to obtain in normal operation of the car. This is especially the case in EMC. I've ever seen some wires topology giving very differents results. Sometimes, fields can be amplified by a resonant circuit as wire and ECU input stage !
That's why standards are defined and gives values which we could find sometime a little severe. Do not foreget that we don't design an ECU and especially a safety one with nose feeling...


Irawan, The power supply I was speaking about in the previous post was designed to work both for 12V and 24 application. It could operate from 5 to 34V. However, for 12V application, the varistor was added to prevent from the load dump. Otherwise, PCB was common. The regulator was LM2576HV-adj. From 5 to 8V, only the CPU and memories were able to operate (3.3V technology). It gives the possibility to the software to work even in 12V application cranking phases.

Regards
Stephane