Why 800 mA and 1.3 V dropout matter for your rail
The LD1117D33CTR is a 3.3 V fixed-output LDO regulator from STMicroelectronics, rated for 800 mA continuous output current with a maximum dropout voltage of 1.3 V at that full load. That dropout number is the headroom you need between input and output — if your input rail dips below 4.6 V, the output starts to sag. For a 5 V bus feeding a 3.3 V MCU rail, that leaves 0.4 V of margin before dropout, which is tight but workable if the 5 V rail is regulated. At higher frequencies the rejection rolls off, so if your input has switching noise above a few kHz, plan for additional filtering on the output.
Package and temperature range for industrial builds
Housed in an 8-SOIC (0.154", 3.90 mm width) package, this is a surface-mount part that reflows on a standard lead-free profile. Compared to the LD39020DTPU33R, which offers 80 dB PSRR at 1 kHz but only 200 mA output, the LD1117D33CTR delivers four times the current. The LDFPVR sibling provides 1 A output and adjustable output with enable and power-good features, but its PSRR is lower (62 dB at 120 Hz). For a fixed 3.3 V rail at 800 mA, the LD1117D33CTR is the simpler, higher-PSRR choice.