Precision shunt reference in a SOT-23-3 footprint
The Texas Instruments LM4040BIM3X-2.5 is a precision shunt voltage reference delivering a fixed 2.5V output with a ±0.2% initial tolerance.
±0.2% tolerance and 35 µVrms noise floor
The ±0.2% tolerance at 25°C sets the initial accuracy floor — a 2.5V reference will sit between 2.495V and 2.505V before temperature drift. For a 12-bit ADC with a 2.5V reference, this noise contributes roughly 0.06 LSB — negligible for most industrial data-acquisition paths, though a 16-bit system may want a lower-noise reference or an external filter cap. As a shunt reference, the LM4040BIM3X-2.5 sinks current through the cathode to regulate the output voltage. The minimum cathode current is 65 µA, and the maximum continuous output current is 15 mA. The design must ensure the series resistor from the supply rail delivers enough current to bias the reference while keeping the total below 15 mA under all load conditions.
NRND — plan for last-time-buy or alternate
The LM4040BIM3X-2.5 carries a Not Recommended for New Designs (NRND) lifecycle status. This means TI has flagged it for eventual discontinuation — new BOMs should not select this part, and existing designs should identify a drop-in replacement or budget for a last-time-buy.