2.048V shunt reference — ±0.5% tolerance in SOT-23-3
The Texas Instruments LM4040CEM3-2.0/NOPB is a precision shunt voltage reference delivering a fixed 2.048V output with ±0.5% initial tolerance. The shunt architecture means it behaves like a two-terminal Zener — it requires a bias resistor from the supply to set the cathode current. The minimum cathode current is 68 µA, and the maximum output current is 15 mA, so the resistor value must keep the device within that window across load and supply variation.
Noise and temperature drift — the so-what for ADC reference duty
Output noise is specified at 35 µVrms over the 10 Hz to 10 kHz band. For a 12-bit ADC with a 2.048V reference, that noise contributes about 0.3 LSB — acceptable for most industrial data-acquisition channels, but a lower-noise reference (e.g., the LM4140 series) would be needed for 16-bit or higher systems. The temperature coefficient is 100 ppm/°C. For precision measurement, a lower-drift reference (e.g., 10 ppm/°C) would be necessary.
The LM4040CEM3-2.0/NOPB is marked obsolete by the manufacturer. Because the part is obsolete, buyers should expect limited and diminishing availability.