What the PSRR figure means for your post-switcher rail
The LM117H delivers 80 dB of ripple rejection at 120 Hz, dropping to 65 dB at the same frequency — this is the line-frequency rejection floor. A switching pre-regulator running at 100 kHz will have its ripple attenuated by roughly 30 dB less at that frequency, so the LM117H works best when the input ripple is below a few hundred kHz. Rated for 1.5 A continuous output with a 40 V maximum input and an adjustable output from 1.25 V to 37 V — the dropout voltage at full load is typically 2 V, so the input rail must stay at least 2 V above the set output voltage across the load range.
Housed in a TO-3 (TO-205AD) metal can, through-hole only — the tab is the output and must be bolted to a heatsink for any load above a few hundred mA. No SMT equivalent exists in this package family. Built-in over-current, over-temperature, and short-circuit protection mean it can survive a momentary output short without external foldback circuitry.
Sourcing and lifecycle — active, no LTB on the horizon
ROHS3 compliant per the manufacturer's declaration — no restricted substances in the bill of materials.