2.048 V shunt reference with ±0.1% initial tolerance
The LM4040A20IDBZT is a shunt voltage reference with a fixed 2.048 V output and ±0.1% tolerance. The shunt architecture means it behaves like a two-terminal Zener: it regulates by shunting current through the cathode to ground. Minimum cathode current is 80 µA, and the device can sink up to 15 mA while maintaining regulation — wide enough to supply the reference input of most SAR ADCs and still leave headroom for the bias resistor.
Noise floor and temperature drift
Output noise is specified at 35 µVrms over the 10 Hz to 10 kHz band — low enough that it won't dominate the ADC's own noise in a 12-bit system at 2.048 V full scale (1 LSB ≈ 500 µV). The temperature coefficient is 100 ppm/°C, so a 50°C swing shifts the output by about 10 mV — acceptable for most industrial control loops but worth derating if the reference sits near a hot regulator or power stage.