60V input ceiling — the high-voltage LM317 variant
The LM317HVK STEEL is the high-voltage member of the LM317 adjustable regulator family, rated for a 60V maximum input — 20V higher than the standard 40V LM317. That extra headroom makes it the natural choice for 48V telecom rectifiers, industrial 48V–57V rails, and any linear supply where the unregulated input can crest above 40V.
1.5A output in a TO-3 — thermal reality
Rated for 1.5A continuous output, the TO-3 steel package (TO-204AA) handles the thermal dissipation. The quiescent current is 12 mA typical — negligible for the load budget but worth noting in always-on bias supplies. With a 1.25V minimum output and adjustable up to 57V, the dropout voltage across the pass element sets the minimum input-output differential; at 1.5A the dropout is around 2.5V typical, so budget the input rail at least 3V above the desired output.
PSRR and protection — clean rails under load
PSRR runs 80 dB at 120 Hz and stays above 65 dB across the line-frequency band — good enough to knock down 100/120 Hz ripple from a rectified AC input before it reaches sensitive analog loads. Built-in over-current, over-temperature, and short-circuit protection mean the regulator folds back safely under a fault; no external crowbar or current-limit resistor needed.
Package and mounting — through-hole TO-3
The TO-3 steel can (TO-204AA, supplier device package TO-3-2) is a two-lead through-hole package with the metal tab as the common ground/heat-sink path. It mounts to a chassis or external heat sink through the two mounting holes; the tab is electrically common with the output (pin 2 in the standard TO-3 pinout). The steel case is heavier than the aluminium TO-3 variants but offers better mechanical ruggedness in high-vibration environments.