The STMicroelectronics LD1117ADT33TR is a single-output, positive fixed LDO regulator delivering a regulated 3.3 V at up to 1 A from a maximum input of 15 V. The 1.3 V maximum dropout at 1 A means the input must stay above 4.6 V to hold regulation at full load; a 5 V rail with 5 % tolerance (4.75 V min) barely clears it, so budget headroom carefully. The 10 mA quiescent current is a standing 33 mW dissipation — fine for a continuously powered industrial rail, but worth noting if the design is battery-sensitive.
Dropout and PSRR — the two numbers that decide fit
The headline dropout of 1.3 V max at 1 A sets the input headroom floor. For a 3.3 V output, a 5 V rail with 5 % tolerance (4.75 V min) leaves only 1.45 V — just 150 mV of margin above dropout. If the input sags under load or during brownout, the regulator drops out and the output follows the input minus the dropout voltage. That's a solid figure for a 1 A LDO in this package class; it means the output ripple from a 1 Vpp input ripple at 120 Hz is attenuated to roughly 180 µVpp — quiet enough for many 12-bit analog chains.