OK, the circuits I want to protect are:
- 12V: LM317 + 22uF (using PTC fuse)
- open drain MOSFETs output
- backup battery connection (using PTC fuse)
- transformer secundary (using MOV)
The main goal is to pass electromagnetic compatibility tests (from CE marking), which involves the EN61000, EN55022 and EN50130 norms.
So protection against:
-ESD
-Radiated imunity
-EFT/B
-Surges
-Conducted RF
-Power frequency magnetic
-voltage dips and interruptions
These tests don't apply to all circuits, but most of them.
About the protection devices, I've read about the new MLV which are varistors with faster response time (<500ps against <25ns for regular varistors) and higher power for smaller smd packages. The only disadvantages to TVS diodes are bigger clamping voltage and still slower response time (1ps for TVS diode).
Size matters, so those big TVS diodes (they have to be big to support higher power) are not suitable for small boards.