I tried to look up this kind of question in the archives but didnt find much usefull information. I also have another question in regards to EMI but I will ask this later in a seperate post.
Currently I am designing a PCB which is actually pretty basic, it has some switches(around 10), some leds, a buzzer and a few other outputs and a microcontroller and it is powered by 2 AA alkaline batteries in series, thus 3V. Product will be tested at a notified body like TUV rheinland, so far nothing really troubling. I have done this before, some issues were discovered and resolved. But this was for EMC according to CE guidelines and was tested with an EMI field strength of 3V/m. Since it is a product to be used in a car I now have to test against automotive EMC and thus against other test levels up to 30V/m. Previous products I tested had to comply with 3V/m, I also did some testing at 10V/m and both products I tested failed but since only 3V/m was required that was ok. Since I am now designing for levels of 30V/m I do expect more issues.
My question actually involves around this issue, I am actually struggling to comprehend how much my design will be affected at these levels of EMI(30V/m). How much will the digital inputs be changed by the field, how about my outputs? Are my pull down/up resistors to weak? How much will my supply voltage be affected? Is there any way I can guess how good my countermeasures to the EMI interference will perform?
To make it a little more concrete I will give an example. I have several digital IO with a pullup of 100k to VCC and a switch to ground. I also have some outputs which need to be able to switch up to 2Mhz so added an RC filter of 1k and 100pF. I can imagine a RC filter of 100R and 1nF might be a stronger filter and harder to affect but it is more a gutt feeling than that I can explain it with hard numbers or facts. Since frequency isnt really important for my switches and thus digital IO should I settle for 1k-100pF filter/100R-1nF RC filter or go high. Perhaps 100R/100nF?