3 A adjustable LDO — dropout and headroom
The LP3876ES-ADJ/NOPB is a positive adjustable LDO regulator delivering up to 3 A continuous output. Maximum dropout is 1.2 V at the full 3 A load — the input rail must stay at least 1.2 V above the programmed output voltage across line and load to maintain regulation. For a 3.3 V output, the input needs at least 4.5 V; a 5 V rail with 10 % tolerance (4.5 V min) is marginal and a 5.25 V minimum input is safer. Quiescent current is 5 mA typical, rising to 15 mA maximum under all conditions. This Iq is higher than a modern CMOS LDO but acceptable for post-regulation where the load current dominates the efficiency calculation.
Thermal and protection — DDPAK package
The DDPAK/TO-263-5 surface-mount package (5 leads plus exposed tab) is designed for power dissipation. On-chip protection includes overcurrent limiting, overtemperature shutdown, and short-circuit current foldback — the regulator survives an output short indefinitely without damage, provided the thermal limit cycles. An enable pin (active high) allows the output to be gated for power sequencing or shutdown; when disabled, the output goes high-impedance and the quiescent current drops to near zero.