I generated a DC/DC PS circuit from Maxim Integrated, and got this output:
You'll notice that both the inductors and the capacitors have their respective resistances marked (in milliohms). Are these values important enough (generally speaking) for me to include them? What is the threshold of precision where it becomes important?
The important question is what do you want to get out the simulation?
If you want to see the basic operation, rough idea of duty cycle, peak inductor current, its probably not important to include parasitics.
If you want to estimate something like efficiency, load regulation, output ripple then parasitics will become more important. Take for example output ripple. This is dictated by the main inductor value and the impedance of the output capacitors. It is not uncommon for the reactance of the capacitors to be smaller than the ESR at the frequency of operation for electrolytic caps. Hence if you don't add a realistic ESR your output ripple voltage ill be completely unrealistic, both in magnitude and overall shape. In your case it appears to be ceramics so not so bad.
A way I like to work is develop the sim without these parasitics, once the basic operation is good then start adding them in. The parts that show ESR values are all the important one. Items like C1 don't need it
One other reason for adding parasitics is to make the simulation work properly. Circuit with inductors & caps and rapid switching can have severe (unrealistic) ringing if there is no loss mechanism.
Usually the parasitics and other values are not displayed as it would clutter the design. If you have a component that you know is going to be differing from application to another (e.g. external power resistor or your sample of a reference circuit to be adopted to another design) you could add requirements as displayed or as notes in the schematic.
Notice that only the elements where the parasitic resistance is critical have this marked. In a switching converter, there are four main places where parasitic elements are important to consider: the input capacitors, the inductor, the switching MOSFETs, and the output capacitors.
In your schematic, C1 and C2 do not have parasitics indicated; these are places where the ESR doesn't really matter to the circuit's functioning. Instead, the ESR is marked on CINB, CIN1, CIN2, L1, COUT1, and COUT2--the input capacitors, inductor, and output capacitors. This circuit doesn't have any switches on it as they're internal to the IC in this case, so you don't have to select ones that will work.
I wouldn't be surprised if EESim showed on resistance and maybe even input capacitance and/or gate charge of switches if you did use an external-switch converter, though. (Or it might bypass all that and just give you a specific part number to use.)
There are a few other places where you need to be careful with parasitics as well, depending on your converter topology. If your topology uses a sense resistor, its parasitic inductance can be significant. The coupling capacitor in a SEPIC will also require a low ESR, and the transformer used in a flyback converter needs to have a high leakage inductance. And of course, any diodes used in non-synchronous converters should be as fast as possible and as low-Vf as possible--Schottky diodes are ideal.
