Fixed 3.3 V rail, 800 mA — the LDO for moderate loads
The STMicroelectronics LD1117F33C is a fixed 3.3 V output low-dropout regulator rated for 800 mA continuous output. Dropout voltage maxes at 1.3 V at full load. The single positive regulator includes over-current and over-temperature protection, and quiescent current runs 10 mA typical.
75 dB PSRR — ripple rejection on the mains-derived rail
Power-supply rejection ratio is 75 dB at 120 Hz, which is the fundamental ripple frequency from a full-wave rectified 60 Hz line. That level of rejection attenuates a 1 Vpp ripple on the input to under 0.2 mVpp at the output — useful for powering analog stages or noise-sensitive loads fed from an unregulated bulk supply.
Industrial temperature range, TO-220 through-hole
The TO-220-3 package with a metal tab can be bolted to a heatsink or chassis — the tab is the output terminal, so the heatsink path is electrically live and must be isolated or accounted for in the layout.
Obsolete — sourcing reality and the replacement path
No official successor is listed on the record. For new designs or volume production, the LD1117 series includes adjustable-output variants and other fixed voltages in the same TO-220 footprint; the base product number LD1118 family may offer a current-production alternative, but pin compatibility and dropout specs should be verified against the specific application.