Fixed 3 V shunt reference for precision bias and ADC references
It operates as a shunt regulator, meaning it sinks current from a series resistor to maintain the output voltage, making it suitable for low-power bias circuits, ADC/DAC reference inputs, and comparator threshold generation.
Noise and drift — the accuracy budget
Output noise is specified at 35 µVrms over 10 Hz to 10 kHz, which sets the noise floor for a 12-bit or 14-bit ADC reference.
The part comes in a SOT-23-3 package (also listed as TO-236-3 / SC-59), a common three-pin surface-mount footprint with 0.95 mm pitch. The small size fits densely populated boards, but the thermal pad is the cathode — the board copper area under the package sets the effective thermal resistance for the 15 mA output current capability.
Cathode current and shunt operation
Minimum cathode current is 82 µA, which is the quiescent current the shunt needs to regulate. The maximum output current is 15 mA, limited by the package dissipation. In a typical application, a series resistor from the supply to the cathode sets the total current — the load plus the 82 µA minimum — so the resistor value must be chosen to keep the shunt in regulation over the full load and supply range.
No official second-source or successor is listed, but the LM4040 family includes multiple voltage options in the same SOT-23-3 footprint for design flexibility.