Precision bias for signal-chain boards
The LM4128BMF-2.0/NOPB is a series voltage reference from Texas Instruments that delivers a fixed 2.048 V output with ±0.2% initial tolerance — tight enough to set the full-scale range for a 16-bit ADC without external trimming. It sinks 100 µA quiescent and can source up to 20 mA to the reference input of multiple converters or a DAC buffer. As a series reference, it regulates the output from the input rail — 2.448 V to 5.5 V — without needing a ballast resistor like a shunt reference would. The fixed output eliminates the noise and drift of an external divider network.
Noise and drift that limit the ADC chain
A 16-bit ADC with a 2.048 V reference has a 31.25 µV LSB; the reference noise alone contributes about 6 LSBs of peak-to-peak noise, so the system noise budget needs to account for it. Temperature coefficient is 75 ppm/°C — over a -40°C to 125°C junction range, the output can shift by roughly 12.3 mV worst-case. That is about 0.6% of the 2.048 V output, which dominates the initial tolerance in a wide-temperature application. For precision across temperature, the tighter 20 ppm/°C LM4132 sibling is a better fit.
SOT-23-5 footprint and sourcing posture
The LM4128BMF-2.0/NOPB comes in a SOT-23-5 package (SC-74A), a 5-lead surface-mount footprint that fits dense mixed-signal boards. The tape-and-reel or cut-tape packaging suits both prototype assembly and production reflow. The part is ROHS3 compliant, meaning no exempt substances and full lead-free assembly compatibility.