The LM4040CIM3X-2.0 is a precision shunt voltage reference from the LM4040 family, delivering a fixed 2.048 V output with ±0.5% initial tolerance. That 2.048 V is a deliberate choice for ratiometric ADC references — it maps cleanly to a 0-to-2.048 V input range, which is common in 12-bit and 16-bit converters running on a 3.3 V rail. The shunt topology means it behaves like a two-terminal Zener: you set the current through it with a single series resistor, and the part regulates the voltage across itself. That resistor value depends on the supply voltage and the load current the reference has to sink — the 15 mA output capability gives you headroom for driving multiple ADC reference inputs or a buffer stage.
Temperature drift and noise — the real-world stability limits
That is fine for a 12-bit system where 1 LSB at 2.048 V is 0.5 mV — you have some margin. For a 16-bit ADC with 31 µV LSBs, that drift eats into your error budget, and you would want a lower-tc part like the LM4040A with 30 ppm/°C.
Package and footprint — SOT-23-3, tape and reel
The part comes in a SOT-23-3 package (TO-236-3 / SC-59 equivalent), surface-mount, supplied on Tape & Reel. The three-pin footprint is standard: cathode, anode, and no-connect. The 65 µA minimum cathode current means the series resistor can be sized for low quiescent draw in battery-powered designs — the reference itself does not waste much current.