1.8V fixed LDO — what it powers
The STMicroelectronics LD1117V18 is a single-output, positive fixed LDO regulator delivering a 1.8V rail from a maximum 15V input. It is rated for 800mA continuous output current, with a maximum dropout voltage of 1.2V at full load — meaning the input must stay above 3.0V to maintain regulation at 800mA. The 75dB PSRR at 120Hz makes this part a candidate for powering 1.8V analog or mixed-signal rails — ADC supplies, PLL VCOs, or sensor front-ends — where line-frequency ripple rejection matters. The 10 mA quiescent current is typical for a bipolar LDO of this output capability.
Obsolete — replacement and sourcing path
For new designs, consider the LD1117 series in the same TO-220 package with a different fixed output voltage — the LD1117V33 (3.3V) or LD1117V50 (5.0V) — or look at the LD1117 adjustable version (LD1117V) if the 1.8V rail can be set with a resistor divider. None of these are drop-in replacements; the fixed output voltage is set internally. No stock-holding claim is made.
The 1.2V dropout at 800mA means 0.96W dissipation at minimum headroom — more if the input is higher. Over-current and over-temperature protection are built in — the regulator folds back or shuts down if the junction exceeds the thermal limit or the output current exceeds the safe area.