Analog vs Digital Sensors
When it comes to sensors I was always an analog guy. Analog sensors put out voltages or currents that are easy to verify with a multimeter. Or if you really need a pretty picture then you can hook up an oscilloscope and see a very complete story. Analog sensors tend to be simple, and have datasheets that tend to be under ten pages long. However, these days, most of the time, analog voltages are going to get run into A/D converters for some further digital domain processing and decision making.
So the chip makers have decided that if the signal needed to be digitized, why bother running the signal into a microcontroller, and perhaps degrading the signal along the way? Why not instead build the A/D converter into the chip and give the customer a signal that has been pre-sliced and pre-diced. And while the chip makers are adding an A/D converter, how about some signal processing and adaptive sensing? Why not build a whole small processor into the sensor to try to give the user options. Perhaps 200 or so options? So simple sensor chips are leveraging their digital interfaces and turning into swiss army knives of options and functionality
And to help the user get acquainted with all those high-powered options, the chips need to have datasheets that explain the options. Sometimes 78 pages long. So you might ask why a 78 page datasheet is necessary just to read some photodiodes with accompanying LEDs? And I guess the answer would be: Yes, we are going to turn on some LEDs and read some photodiodes, but with lots of options and flexibility for various users and applications.