The Texas Instruments LM4040BIM3-8.2 is a precision shunt voltage reference that delivers a fixed 8.192V output with ±0.2% initial tolerance. The SOT-23-3 package fits into tight layouts where board space is at a premium, and the shunt topology means it only needs a single resistor to set the bias current, no external pass transistor.
That means TI has flagged it for eventual discontinuation — no new production builds should start with this order code. If you're qualifying a new design, look at the active LM4040 family siblings with the same 8.192V output and ±0.2% tolerance in the SOT-23-3 package — the footprint is identical, so the board spin is zero.
The 8.192V output is a common reference voltage for 12-bit and 16-bit ADCs that use a 2.048V or 4.096V internal reference multiplied up — or directly as the top of a resistor divider for a 0-10V analog input. The ±0.2% tolerance means the initial output error is at most 16.4 mV, which for a 12-bit system with a 10V span is about 0.16% of full scale — well within the LSB budget. The 15 mA output current is enough to drive the reference input of a single ADC plus a small bypass cap; if you're splitting the reference to multiple converters, you'll need a buffer. The 95 µA minimum cathode current sets the lower bound on the bias resistor — at a 12V supply, a 40 kΩ resistor gives about 100 µA, which is just above the floor and keeps the reference in regulation.