What the PSRR rating buys you on the LM317P
The LM317P delivers 80dB ~ 65dB of PSRR at 120Hz. That ripple rejection matters when the input rail carries rectified line-frequency ripple — the regulator knocks it down by a factor of 10,000 at 120Hz, so the output stays clean enough for sensitive analog loads like instrumentation amplifiers or ADC references.
Output current and thermal budget for the TO-220FP
Rated for 1.5A continuous output. At 1.5A with a 10V input-output differential, you are dissipating 15W; plan a heatsink with a thermal resistance low enough to keep the junction below 125°C.
Input voltage range and protection features
Maximum input voltage is 40V; output adjusts from 1.2V up to 37V. Built-in over-current, over-temperature, and short-circuit protection mean the regulator survives a momentary output short without external clamp diodes — useful for benchtop supplies or test jigs where the load is unpredictable.
Active lifecycle status — STMicroelectronics still produces the LM317P.