Pet peeve: leakage current missing from inputs. So often I've seen regulators with ~1k resistors when 100k+ would do; why waste power unnecessarily?!
Conversely, if it's not documented, then give some justification why: for example is there an internal impedance to model? (Example, internally voltage-mode compensated regulators. Some, the impedance between pin and error amp is itself a transfer function; others, it's the summing node so you need to size the divider resistors appropriately, or any other pole-zero elements as needed.) In that case, give the equivalent circuit (typically RLCD level, or maybe the first row of transistor(s) connected to it).
Alternately, are components of recommended type and range connected to it, and, just don't worry about the pin characteristics, do as you're told?
It doesn't
have to be explanatory; I can settle for an instruction, an order. But it needs to be broad or flexible enough to cover the possible range of application for the device; I'll most likely keep shopping if I find something too limited and opaque. Conversely, trying to account for every possible application (within reason), is a lot of up-front work, and you probably don't want to go to those lengths (or have the department budget and resources to do so). In that case, give enough information that one can reasonably figure it out.
Classic era TI datasheets were pretty good about this (or maybe I'm thinking of National?), like with equivalent diagrams. Whereas they've been pretty shite about both of these in the modern era.
...Do manufacturers do research and prototyping labs anymore? I mean of the sort like the classics played around with. Like how the LM13700 datasheet has
dozens of applications, because, well it has to, it's a somewhat unusual part (it's not your bog standard op-amp), but also those were well-known and practical applications for the function at the time. Ditto the LM393 and such, lots of ways you can use a comparator. Some of those were well-known from earlier application (LM13700 is an integrated OTA, improving on discrete circuits used through the 60s), some of them are just, hey put some techs and engineers into a room, here's the functional schematic, here's some functional behavior, go nuts, figure it out, use it, abuse it, see what works. Come up with ideas, cull the more ludicrous ones for practicality ("let's use the inputs as an ESD array!"), parameter variance / ratings abuse (plausible functionality but not part of design / process optimization), or conversely if something of sufficient interest is found, maybe back-propagate it to the spec, and design and test for it; etc.
...This probably goes well beyond scope of your position, but to the extent you can effect such change, or promote such ideas to the higher-ups that can, maybe some good can come of it. If nothing else, just to say: to open your own perspective to wider applications, and how many things need to be known about each pin for example, and thus guide what kind of specifications, descriptions and applications go into your documents.
...Also the perennial: Why do Application Notes suck SO BAD?
And yeah, this is definitely a tricky writing problem; I sympathize. Helps to have fresh or blank eyes on the project; bring in beta testers (as it were) who don't know much of anything about the chip you're working with. Ask them to make a design, then you review it and see how well they did. Adjust documents, test again -- retesting with the same people may provide different insights to testing with new "blank" people, but I would guess generally prefer blank. And yeah, that's going to be a lot of work, maybe call this the belt-and-suspenders method, and maybe it can be "cheaped out" to varying degrees, but getting more eyes on it in any case will definitely help you see what biases and assumptions you were writing from.
Tim