A 2.048 V shunt reference in a TO-92-3 — what the TO-92 means for the board
The Texas Instruments LM4040EIZ-2.0/NOPB is a precision shunt voltage reference with a fixed 2.048 V output, ±2% initial tolerance, and a 15 mA output current capability. The shunt topology means it sinks current from the supply through an external resistor; the cathode current floor is 70 µA, so the resistor must be sized to deliver at least that much at the minimum supply voltage. The TO-92-3 through-hole package is the legacy form factor — it stands off the board and is hand-solder or wave-solder only. No MSL rating applies because the package is not moisture-sensitive, but the leads need a clean solder joint to avoid intermittent contact in high-vibration environments.
Tolerance and temperature drift — the ±2 % and 150 ppm/°C reality
The ±2 % tolerance on the 2.048 V output means the reference voltage can sit anywhere from 2.007 V to 2.089 V at 25 °C. That is acceptable for an 8-bit ADC reference with a 5 V span, but marginal for a 12-bit system that expects better than 1 LSB at 2.048 V.