Adjustable LDO for noise-sensitive rails
The LM2931D-R is a single-output, adjustable positive LDO regulator from Texas Instruments, delivering up to 100 mA. Its 80 dB PSRR at 120 Hz makes it a strong candidate for cleaning up supply ripple on analog or mixed-signal boards — the kind of rail that powers an op-amp front-end or a reference buffer where line-frequency hum would otherwise couple into the signal path.
Dropout voltage and headroom planning
Maximum dropout is 0.6 V at the full 100 mA load. The input rail must stay at least 0.6 V above the programmed output voltage to keep the pass element in regulation. One part number covers multiple rails on the same BOM — useful when a design needs different output voltages from a common LDO footprint, as long as the input voltage stays below the 26 V absolute maximum.
Temperature range and protection features
On-chip current limit and thermal shutdown protect the regulator and downstream circuitry during a sustained overload or a short to ground.
Obsolete — sourcing through independent distribution
Texas Instruments lists the LM2931D-R as obsolete. No official successor or pin-compatible replacement is recorded on the product status line.