I am working with an existing schematic which has bidirectional TVS surge protection, laid out like this:
The TVS diodes are discrete and have different breakdown voltages. To me, the above configuration makes less sense than:
These connections make more sense since there is no 'extra' 0.7V (or whatever the forward drop is for the diode) added to the breakdown voltage of the reverse-biased diode, which someone may forget.
Is there any particular reason for putting two discrete TVS diodes in 'series', like the above schematic rather than 'parallel'?