What rail range does this part cover?
The LM317LD13TR is an adjustable positive linear regulator from STMicroelectronics that delivers 100 mA output from a 1.2 V minimum up to 37 V maximum, supplied by a 40 V maximum input rail. That range spans the common analog supply voltages — 3.3 V, 5 V, 12 V, 24 V — from a single regulator, which simplifies BOM consolidation for mixed-voltage boards.
PSRR and ripple rejection — what the 80 dB figure means
The PSRR is specified at 80 dB typical falling to 65 dB, both at 120 Hz — the fundamental of full-wave rectified mains. This tells you the regulator attenuates 100/120 Hz ripple by a factor of 10,000 to 1,800, which is the margin that keeps a sensitive analog front-end (audio, measurement bridge) clean of hum. At 120 Hz, the 80 dB figure is meaningful for designs where the unregulated input carries significant residual ripple from a linear transformer supply. For switching pre-regulators the ripple frequency is higher, and this IC's PSRR typically rolls off above a few kilohertz — factor that into the noise budget.
Protection features built in
On-chip over-current, over-temperature, and short-circuit protection are included — no external clamp diode or foldback circuit required for basic fault containment. The 5 mA quiescent current is the price of the internal reference and protection; it does not vary much with load, so the no-load dissipation is predictable.
Supplied in an 8-SOIC (0.154", 3.90 mm width) surface-mount package, available on tape-and-reel or cut tape. Lifecycle status is active — STMicroelectronics lists this part as current production with ROHS3 compliance.