2.048V shunt reference — what it does for your rail
The LM4040D20QDBZR is a fixed 2.048V shunt voltage reference from TI's LM4040 series. It regulates by shunting current through the cathode to ground — no series pass transistor, no dropout voltage. The 80 µA minimum cathode current sets the bias resistor: for a 5V rail, (5V - 2.048V) / 80 µA = ~37 kΩ minimum. The shunt topology means it can sink up to 15 mA without an external pass device, which is enough to bias multiple ADC reference inputs or comparator thresholds on the same rail.
Tolerance and temperature drift — fit for the accuracy budget
Initial tolerance is ±1% — at 2.048V that's ±20.5 mV worst-case at 25°C. The temperature coefficient is 150 ppm/°C, adding about ±0.3 mV per 10°C shift. For a 10-bit ADC with a 2.048V reference, that's roughly ±1 LSB of drift over a 50°C window. It won't satisfy a 16-bit precision chain, but for general-purpose monitoring, comparator thresholds, and bias generation it holds the line without a precision op-amp buffer.
TI lists the LM4040D20QDBZR as Active. The base product number is LM4040, which spans multiple voltage options and tolerances across the SOT-23-3 footprint. If the 2.048V ±1% is the BOM target, this part is a clean fit for new and sustaining production — no supply-chain clock to manage.
SOT-23-3 package — board-fit checklist
Three pins: cathode, anode, and a no-connect. Surface-mount only. The 0.95 mm pin pitch is standard for SOT-23; no exotic footprint required.