AEC-Q100 shunt reference for automotive sensor rails
The Texas Instruments LM4040QAIM3-2.5/NOPB is a 2.5 V precision shunt voltage reference with AEC-Q100 automotive qualification, in a three-pin SOT-23-3 package. It delivers a fixed 2.5 V output with ±0.1% initial tolerance and 100 ppm/°C temperature coefficient, drawing a minimum cathode current of 65 µA and capable of sinking up to 15 mA.
±0.1% tolerance and 100 ppm/°C — what it buys the BOM
The ±0.1% initial tolerance holds the output between 2.4975 V and 2.5025 V at 25 °C, which is tight enough to serve as a reference for a 12-bit SAR ADC without an external trim.
15 mA output and 65 µA cathode current — load planning
The 15 mA maximum output current sets the ceiling for how many loads this single shunt reference can drive. A typical automotive ADC reference input draws 200 µA to 500 µA, so one LM4040QAIM3-2.5/NOPB can feed a dozen ADC channels plus a comparator threshold network before hitting the current limit. The minimum cathode current of 65 µA means the bias resistor must be sized to keep at least that much current flowing through the reference at all times — if the load drops below 65 µA, the output voltage drifts out of regulation.