Adjustable LDO with 80 dB PSRR floor
The LM317LIPKG3 is a Texas Instruments adjustable positive LDO delivering up to 100 mA from a 38 V input rail. Its PSRR holds 80 dB at 120 Hz, rolling to 65 dB — a meaningful margin for cleaning switching-regulator ripple before it reaches a sensitive analog load. Output voltage adjusts from 1.2 V to 32 V via two external resistors, matching the classic LM317 topology in a surface-mount SOT-89-3 footprint.
PSRR profile and quiescent current
At 120 Hz the PSRR starts at 80 dB and degrades to 65 dB — the 15 dB delta across frequency is typical of a three-terminal LDO without a separate bypass pin. The 2.5 mA quiescent current is a trade-off for that ripple rejection; a lower-Iq LDO would sacrifice PSRR at the same corner. Protection includes over-current, over-temperature, and short-circuit shutdown — the three-terminal design relies on internal thermal limiting rather than an external enable pin.