The L7805CDT-TR is a fixed 5V positive linear regulator from STMicroelectronics, rated for 1.5A continuous output. The DPAK (TO-252) surface-mount package means the tab is the output node and the primary heat path — if the board layout skips the copper pour under the tab, the thermal shutdown will cycle before you reach 1.5A. PSRR is 62 dB at 120 Hz — that's the ripple rejection on the 5V rail for a full-wave-rectified input. For an analog supply feeding an op-amp or ADC reference, that 62 dB keeps 120 Hz ripple down to a few millivolts at the output.
Dropout, quiescent, and the thermal budget
Maximum dropout is 2V at 1A load, typical is lower. That means you need at least 7V on the input to hold regulation at full current — budget 8V for margin. Quiescent current is 8 mA, which is the overhead the regulator burns even with no load; on a battery-powered board that 8 mA is a standing drain. Input voltage max is 35V — don't push it past that; the absolute max is higher but the safe operating area shrinks fast above 35V.
The L7805 base number has been in production for decades.