1.5A adjustable LDO — dropout and headroom
The LP3965ES-ADJ/NOPB is a positive adjustable LDO regulator delivering 1.5A continuous output from a 1.216V minimum to 5.1V maximum. Single regulator with positive output configuration and enable control — the enable pin lets the system power-sequence the rail or shut down the regulator to 9 mA quiescent current (Iq).
PSRR and noise-sensitive analog rails
Power supply rejection ratio is specified at 60 dB to 40 dB at 120 Hz — this is the ripple rejection from a full-wave rectified input or a switching pre-regulator running at line frequency. At 60 dB, a 100 mVpp ripple on the input is attenuated to 100 µVpp at the output; at 40 dB the same ripple passes 1 mVpp. For an analog front-end or ADC reference rail, the lower rejection at higher frequencies means the upstream switcher's fundamental and harmonics need to stay below the regulator's crossover, or a post-filter is required.
Industrial temperature range and protection
The protection set includes over-current, over-temperature, and short-circuit shutdown; the part folds back or latches off rather than letting the pass element fail shorted, which is the failure signature that takes down the downstream load.
DDPAK package — thermal and board integration
Supplied in a DDPAK/TO-263-5 surface-mount package (5 leads plus exposed tab). The tab is the output and the primary thermal path — the datasheet's RθJA assumes a minimum copper area on the PCB, typically 1 in² on the top layer tied to the output node. Without adequate copper, the junction temperature rises above the 125°C limit at full load in a 25°C ambient. The package ships in tube format.