2.5 V reference for precision rails — what the ratings mean
The Texas Instruments LM4128AMF-2.5/NOPB is a series voltage reference that delivers a fixed 2.5 V output with ±0.1% initial tolerance. That tolerance is the BOM's accuracy floor — it sets the worst-case error budget for an ADC reference input, a comparator threshold, or a DAC's full-scale voltage before any temperature or aging drift is added. Input voltage range is 2.9 V to 5.5 V. Temperature coefficient is 75 ppm/°C. Output current is rated at 20 mA. That's enough to drive one ADC reference input plus a 0.1 µF bypass cap, or a single op-amp's reference pin. Driving multiple converter reference inputs or a heavy load (e.g., a resistive divider string below 125 Ω) will pull the output out of regulation — add a buffer amplifier if the load exceeds 20 mA. Supply current is 100 µA typical. That's low enough for battery-powered instrumentation — the reference itself won't dominate the power budget in a sensor node running at a few mA total draw. The SOT-23-5 package is a five-pin surface-mount footprint.
Active production — no LTB clock
No last-time-buy notice, no NRND flag. RoHS3 compliant and lead-free — no exemption issues for EU or California markets. The NOPB suffix confirms the part is fully green, no Pb in the solder finish.
Where it fits — and where it doesn't
This reference fits industrial sensor interfaces, loop-powered transmitters, automotive ECU reference rails, and battery-powered instrumentation.