3V shunt reference with ±0.1% initial accuracy
The Texas Instruments LM4040AIZ-3.0/NOPB is a precision shunt voltage reference delivering a fixed 3V output with a tight ±0.1% initial tolerance. This is the spec that decides whether the reference holds the ADC or DAC transfer function within budget without a trim pot.
Noise floor and temperature drift
Output noise is specified at 35 µVrms over the 10 Hz to 10 kHz band, which keeps the reference from adding jitter to a 12-bit or 14-bit conversion chain.
Cathode current and shunt operation
As a shunt reference, this part regulates by sinking current through the cathode. The minimum cathode current is 67 µA, and the maximum continuous output current is 15 mA. That means the series resistor from the supply rail must be sized to deliver at least 67 µA to the cathode at all times while keeping the total current below 15 mA under worst-case load.
TI no longer manufactures this specific variant.
TO-92 package — rework and retrofit
The TO-92-3 through-hole package is a three-lead inline format with 0.100-inch lead spacing. It drops into existing boards with plated through-holes and is straightforward to hand-solder or wave-solder. No hot-air rework needed — just a soldering iron and a desoldering tool if the old part comes out.