Fixed 1.2V rail LDO — 800 mA, SOT-223
STMicroelectronics LD1117S12CTR is a fixed 1.2V-output low-dropout linear regulator delivering up to 800 mA continuous current. The 1.3V maximum dropout at 800 mA means the input rail needs at least 2.5V to hold the output in regulation — budget that headroom when cascading from a 3.3V or 5V bus. Ripple rejection is 75 dB at 120 Hz, which is adequate for smoothing line-frequency ripple after a rectifier or switching pre-regulator. The quiescent current runs 5 mA — not a low-Iq part, so it's better suited for always-on rails than battery-idle circuits.
Dropout margin and thermal budget
At 800 mA with 1.3V dropout, the power dissipated in the SOT-223 package is about 1.04 W. Protection includes over-current and over-temperature shutdown. No reverse-current or reverse-voltage protection is listed, so an output capacitor with a series diode is recommended if the input can collapse faster than the output.
Active production — order to quote
No stock-holding claim; availability and current pricing confirmed per RFQ.