PDF schematic labelled only as Dell 3440, probably a Latitude or Inspiron model, with no board number or revision in the name. The 2.09 MB drawing should cover the power rails, charger, EC and interface circuits used during board-level diagnosis. Because the ODM and board number are not stated, open the title block to find them and compare them with the number silkscreened on your mainboard before trusting component values.
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 @cidschematicandboardviewofficial. 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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)