Fixed 1.8 V rail, 1 A continuous — the dropout ceiling at full load
The LMS8117AMPX-1.8 is a fixed 1.8 V positive-output LDO from Texas Instruments, rated for 1 A continuous output current. Below that headroom the output falls out of spec. Quiescent current is 5 mA typical, and the maximum supply current is 10 mA. The 60 ~ 75 dB PSRR at 120 Hz gives useful ripple rejection on the output for noise-sensitive analog loads — a sensor or ADC front-end powered off this rail sees less 120 Hz hum from a rectified mains supply.
SOT-223 package and board-fit realities
Packaged in SOT-223 (TO-261-4, TO-261AA) for surface-mount assembly. For a 1 A load at 1.25 V dropout, the die dissipates 1.25 W; a 1 oz copper pad of at least 500 mm² on the top layer keeps the junction below the 125 °C ceiling. Operating temperature range is 0 °C to 125 °C — suitable for commercial and industrial environments where the ambient stays above freezing. Below 0 °C the output accuracy is not characterised; if the board sees cold start, a wider-temp LDO is needed.