I'm planning a design where we'll use PoE to power a data acquisition board (essentially, an ADC + microcontroller + ethernet PHY and interface).
I look at DC/DC isolated converters to get the 5V or 3.3V from the, say 48V from the PoE wires, and I get a headache! I look at two reference designs (from TI and from Analog Devices / LT), and they have a components count of about 50 parts !!!! The Art of Electronics (3rd Edition), on Figure 9.83 show a "real world" example of a switching converter (in that case, it is AC/DC, but same principle), with approx. 40 parts, and they say that that is a "relatively uncomplicated" circuit .....
On the other hand, I see single-package DC/DC converters such as the CUI PDQ10-Q48-S_X_ — 1-inch by 1-inch by 10mm height, 10W, input DC between 18V and 75V. I don't see why something like this would not work. Any comments?
As a secondary question: I guess I will at least want to put the recommended EMI input filter (C-L-C, as per datasheet suggested circuit), and some TVS (say, a 60V or 70V Zener TVS?) just after the output of the rectifier bridge from the ethernet isolation transformers? Any other aspects I need to pay attention to?