Precision shunt reference for 8.192 V rails
The Texas Instruments LM4040A82IDBZR is a precision shunt voltage reference delivering a fixed 8.192 V output with a ±0.1% initial tolerance. This specific voltage is commonly chosen as a reference for 12-bit and 14-bit ADCs where the full-scale input matches 8.192 V, or as a stable bias for precision analog circuits. The shunt topology means it behaves like a two-terminal Zener — it requires a series resistor from the supply and sinks current to regulate the output, making it simple to use but thermally dependent on the cathode current.
Temperature drift and noise budget
Noise from 10 Hz to 10 kHz is specified at 130 µVrms, which is low enough for a 12-bit ADC reference but may need a bypass cap for a 14-bit or higher converter.
Current handling and shunt operation
The device can sink up to 15 mA continuously, with a minimum cathode current of 110 µA to maintain regulation. The series resistor value must be chosen so that the cathode current stays within this window across the full load and supply variation — a common mistake is undersizing the resistor, which starves the reference and drops the output voltage.