Datasheet in PDF format for the NCP81243, about 413 KB. The name gives only the part number and the -D document suffix, which is typical of ON Semiconductor datasheet naming. Datasheets like this give the pinout, package, typical application circuit, electrical limits and pin functions. Repair technicians check them to see which pins carry the input supply, enable, feedback and output signals, so they can measure the right points when a regulator or controller fails to start.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @ic_mosfet_pdf_datasheets. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.