Such a task is perhaps one of the more inconvenient in the present environment, owing to inconsistent terminology across vendors, difficulties in parsing lengthy feature sets, presenting the same for selection in a manner that’s coherent and intuitive, and the innate complexity of the devices themselves complicating all of that.
As a practical matter, existing familiarity with a given product ecosystem can be quite advantageous compared to starting over learning a new one, and public availability of support materials suitable for the level of abstraction at which you wish to approach your development can be useful signals for narrowing the field. Some vendors are more developer-friendly than others.
As for the example given, defining more precisely what is meant by a TFT/LCD controller would be a useful starting point; screens come in a variety of sizes, formats, and interfaces these days.
Understanding the application and its requirements comes first. The concept of “design margin” is meaningless unless the denominator in the equation is defined.
That said, understanding how component ratings are derived and what they actually mean in context of a given component type is important. Different capacitor types have different derating guidelines for example, and for different reasons.
Voltage ratings typically derive from dielectric breakdown phenomena, e.g. a point at which electrons forge a desire path between points A and B, causing prompt and irreparable damage in the process. One does well to observe such limitations strictly.
Power and current ratings typically derive from thermal considerations, with different component families having their own rating conventions that vary from reasonably conservative in the case of inductors, to borderline in case of many resistors, to highly impractical in the case of many FETs. Footnotes indicating test conditions applicable to a given specification are in many cases just as important as the information itself.
Some condensed resources highlighting considerations relative to basic R,L, and C components may be found linked here, and a post highlighting the importance of careful interpretation should be found here.
It’s closely akin to grocery shopping:
- Decide what you want to make and what you need to make it
- Consult recipes from others as needed
- Go to the grocery store, and see what products are available
- Return to point 1 and iterate on the basis of the results from point (3) as needed.
DigiKey is a distributor of electronic components, in a similar manner as one’s local grocery store is a distributor of food items. Presenting products in a way that facilitates comparison, selection and discovery, having stock available for immediate purchase, and offering sale in quantity less than a manufacturer’s order minimums are all services that distribution provides.
The analogy is quite direct, and most reasons why one might articulate for engaging at a grocery store versus individual food item suppliers individually (or vice-versa) transfer quite nicely.
Again, it’s based on assessment of an application’s requirements. Interplay exists among most/all of the factors mentioned, and they’ll carry different weights depending on where the application exists on the spectrum between a one-off build for a dog’s holiday costume and a life-safety medical device selling a million units annually.
If at all.
The temptation to trust it (improperly) as an information source seems too tempting for many/most, it’s more likely than usual to offer bad info in areas of technical specialty, and as a student of such a field one is by definition lacking the discernment needed to recognizebad information.