Calculating a burden resistor for a current transformer
Calculating the burden resistors for a commercial current-transformer is generally quite easy:


Download current-transformer datasheet.
Use values from datasheet.




Chose the burden resistor that produces the desired voltage range for the current range you want to operate in.

Alternatively, if you really want to use your own burden resistor, the datasheet has that formula for you too!

\$E_{O} = I_{P} * \frac{R_{B}}{T_{R}}\ \$  where \$E_{O}\$   is the output voltage, \$I_{P}\$  is the current that will produce the voltage you want, \$T_{R}\$  is the transformer's turns-ratio, and \$R_{B}\$ is the burden resistance, in ohms.

As usual, read the datasheet. Most of your questions appear to be answered in the datasheet for the part you have apparently already chosen!



The reason the reference design you're looking at does not specify any of the parameters for the current-transformer is because it's designed to work with most any current transformer. You are expected to look up the relevant information on your current transformer.



Since you're only interested in single-phase metering, I'd just dump the CT entirely, and just use a shunt-resistor. I think that demo schematic has both just so you can try either, not because they're actually needed.

It's using a CT to get the needed isolation from the high-side of the mains. Since the circuit is referenced to one side of the AC mains, they can't easily use a shunt-resistor on the other side. The CT is a convenient, pre-isolated way to achieve this, but unless you're interested in multi-phase metering or something, it's rather overkill.