2.5 V shunt reference with ±0.2% initial accuracy
The ±0.2% initial tolerance and 100 ppm/°C temperature coefficient place it in the 'B' grade of the LM4040 family — tight enough to serve as the reference for a 12-bit ADC without external trimming, or to set the threshold in a precision comparator circuit.
Shunt topology — bias resistor sets the operating point
As a shunt reference, the LM4040B25IDBZTG4 regulates by sinking current through a cathode-to-ground path. The minimum cathode current is 80 µA; the maximum continuous output current is 15 mA. The external series resistor from the supply to the reference's cathode must be sized to deliver at least 80 µA to the reference while supplying the load, and no more than 15 mA under worst-case supply and load conditions. The 35 µVrms noise spec over 10 Hz to 10 kHz is the integrated wideband noise — useful for estimating signal-to-noise ratio in a data-acquisition chain.
The SOT-23-3 package is a standard, widely stocked footprint, and the tape-and-reel delivery suits automated pick-and-place assembly.