Fixed 8V rail in a DPak
The UA78M08CKVURG3 is a fixed 8V output linear regulator from Texas Instruments, delivering up to 500 mA in a TO-252-3 (DPak) surface-mount package. It's a single-positive-output LDO with overcurrent, overtemperature, and short-circuit protection built in.
PSRR at 120 Hz — what it means on a clean DC rail
The 80 dB PSRR at 120 Hz tells you this regulator attenuates full-wave-rectified ripple (100/120 Hz from a 50/60 Hz mains transformer) by a factor of 10,000. If your unregulated input has 1 Vpp of 120 Hz ripple, the output sees about 100 µVpp — clean enough for most analog front-ends running off an 8 V rail.
Dropout and input range
Maximum dropout is 2 V at 350 mA load — keep the input at least 2 V above the 8 V output to stay in regulation. Input can go up to 25 V absolute max, so it tolerates a 12 V or 15 V unregulated bus without an extra pre-regulator.
Thermal and package fit
The TO-252-3 (DPak) has an exposed tab on the bottom — that tab is the output (Vout) and the main heat path. Solder it to a copper pour on the PCB; the tab's thermal resistance to ambient drops with the copper area. Operating range is 0°C to 125°C junction, so it's a commercial-temp device — fine for indoor gear, not for under-hood or freezer environments.