EMI: which controller is 'immune'

Much more important than which processor you choose, is the design around it - good interfaces & filtering to prevent EMI issues getting to the processor, and causing these "glitches".

Any family will do. All the problems you mention are caused by improper hardware design (PCB layout, filtering). I have made a small board (90 x

66mm) with an ATmega162. Four inputs with optocouplers, three outputs (RS422, RS232) with rc filters (10 Ohm, 10nF) and one 4.7uH common mode filter on the power supply. The PCB is double layer and most of the bottom layer is groundplane. Where the groundplane is open, there is no power supply trace on the top layer and the larger openings are never under an IC. This board passed all IEC945 tests, which included RF field 10V/m from 80MHz to 1GHz, conducted RF of 3Vrms from 150kHz to 80MHz on all ports, fast transients on all ports (1.2kV, 50ns pulses, at 5kHz, 15ms bursts every 300ms) and ESD at 8kV contact discharge and air discharge. No problem detected.

Meindert

Excellent. Would it be possible to see the layout of the board, possibly on a.b.s.e?

How many versions did it take you to get it correct?

martin

Yep, it's there as "Board MPX-SB"

Only 2. It was a design we already had, which complied with EN61000-6-1 and EN61000-6-3 (EMC, domestic/light industrial). One large customer required EN60945/IEC945, so they tested it and we added one Würth common mode filter (rectangle marked L1 in the bottom right corner) in the power supply to meet the requirements. EN60945 requires very high surpression of RF emissions on certain marine frequencies.

Meindert

Thanks. It hasnt turned up on

yet. I'll keep trying

martin

I think you'd better access a newsserver directly. Much faster.

Meindert