Precision 3V shunt reference in a SOT-23-3 footprint
The Texas Instruments LM4040AIM3-3.0/NOPB is a precision shunt voltage reference delivering a fixed 3V output with ±0.1% initial tolerance. It operates as a two-terminal shunt (Zener-mode) device, requiring only an external series resistor to set the bias current.
What the ±0.1% tolerance and 100 ppm/°C drift mean for your BOM
The ±0.1% initial accuracy means the output voltage at 25°C is within 3 mV of 3.0 V — tight enough for a 12-bit ADC reference without external trim. For a 10-bit or 12-bit system this is well within the LSB budget; for a 14-bit or higher system the drift may need a software calibration or a tighter-grade (A or D) variant. The 35 µVrms noise (10 Hz to 10 kHz) is low enough that it won't dominate the noise floor of a 12-bit SAR ADC with a 3V reference input. If the reference feeds a 16-bit ADC or a sensitive PLL bias, an external 0.1 µF bypass cap at the output pin further knocks down the wideband noise.
Shunt topology — design note for the BOM engineer
Because this is a shunt reference, the load current plus the minimum cathode current of 67 µA must flow through the external series resistor at all times. The 15 mA maximum output current sets the upper limit on total current through the device. If the load draws less than the minimum cathode current, the reference may drop out of regulation — so a pull-down resistor or a dummy load may be needed in very light-load designs. The SOT-23-3 package (TO-236-3, SC-59 compatible) shares the same pinout as most other SOT-23 shunt references, so a board layout designed for a LM4040 or similar part accepts this device without a PCB change.