The LD1117V33 is a fixed 3.3V LDO from STMicroelectronics rated for 800 mA continuous output. Its 75 dB PSRR at 120 Hz means it knocks down the 100/120 Hz ripple from a full-wave rectifier by a factor of ~5600 — relevant if this rail feeds an analog front-end or a sensor bias that cannot tolerate ripple on the supply.
800 mA output with 1.2 V max dropout — thermal budget check
Maximum dropout is 1.2 V at full load, so the input rail needs at least 4.5 V to hold 3.3 V regulation. At 800 mA the power dissipation in the TO-220 package is roughly 1 W per volt of headroom — a 5 V input gives about 1.36 W. The TO-220 copper tab can sink that with a modest heatsink or a good ground-plane pour; without one the junction climbs toward the 125 °C ceiling fast.
Active production — no obsolescence watch for new BOM lines
Lifecycle status is Active. ROHS3 compliant. STMicroelectronics lists no successor or end-of-life notice for this base number.
Over-current and over-temperature protection — built-in fault tolerance
On-chip protection folds back current and shuts down die temperature above the safe limit. The quiescent current is 10 mA — not a low-Iq part for battery gear, but fine for a fixed industrial or appliance rail where the load current dominates the power budget.