What this fixed 2.5V LDO brings to a rail
The LD1117S25TR is a single-output positive LDO from STMicroelectronics, delivering a fixed 2.5V at up to 800mA. The 1.2V max dropout at full load means the input rail needs to stay above 3.7V to hold regulation — budget that headroom when selecting the upstream supply. PSRR is 75dB at 120Hz, which filters line-frequency ripple well for analog or mixed-signal loads.
Dropout, protection, and temp range for the BOM
Dropout voltage max is 1.2V at 800mA output — that is the worst-case headroom the input rail must provide over 2.5V. The input can go up to 15V, so the part tolerates a wide upstream swing, but the dropout figure is what sets the minimum operating input. Built-in over-current and over-temperature protection mean the regulator folds back or shuts down before the die sees thermal runaway — no external crowbar needed. Operating temperature is 0°C to 125°C, which covers commercial and most industrial ambient conditions, though the junction temp rise from 800mA in SOT-223 will push the die well above ambient.
Sourcing and compliance — active, ROHS3, tape-and-reel
Supplied in Tape & Reel (TR) and Cut Tape (CT) options, SOT-223 package (TO-261-4, TO-261AA).