The Texas Instruments LM4040AIM3X-3.0/NOPB is a precision shunt voltage reference that delivers a fixed 3V output with a tolerance of ±0.1% — tight enough for most 12-bit ADC references and comparator thresholds without trimming. It is a shunt (two-terminal) reference, so it behaves like a Zener diode: you bias it through a resistor from a higher supply rail, and the reference regulates the voltage across itself.
Noise floor and temperature drift — the real-world limits
That is clean enough for a 3V rail feeding a 16-bit SAR ADC if the reference input bandwidth is comparable. The temperature coefficient is 100 ppm/°C, so from 25°C to 85°C the output can shift by about 18 mV worst-case — something to budget for if the reference sits near a hot regulator or a power stage.
Biasing and current budget
This is a shunt reference with a maximum output current of 15 mA and a minimum cathode current of 67 µA. The bias resistor must be sized to supply the total current — the reference's own cathode current plus any load current — while keeping the shunt current above 67 µA to maintain regulation. For a 3.3V rail feeding a 1 mA load, a 20 Ω resistor works; for a 5V rail with a 10 mA load, the resistor drops to about 130 Ω. The power dissipation in the SOT-23-3 package limits the practical bias to about 10 mA continuous at 85°C ambient.