1.5A LDO for noise-sensitive power rails
The LP38855S-1.2/NOPB is a fixed 1.2V output linear regulator rated for 1.5A continuous output current in a DDPAK/TO-263-5 package, suited for post-regulation of switching supplies feeding analog or mixed-signal loads. Maximum dropout voltage is just 0.18V at the full 1.5A load, meaning the input rail needs only 1.38V minimum to maintain regulation — a narrow headroom that keeps the LDO efficient even when the upstream buck converter sags under transient. Power supply rejection spans 80 dB at 120 Hz down to 65 dB at 1 kHz, filtering the bulk of 100/120 Hz ripple from a rectified front-end or the switching fundamental of a downstream converter.
Thermal and protection envelope
Built-in protection includes over-current, over-temperature, short-circuit, and under-voltage lockout — the UVLO prevents the pass element from operating in the linear region during input ramp-up, avoiding output overshoot. Quiescent current is 300 µA typical and supply current maximum is 15 mA, so the regulator's own draw stays low enough for always-on rails in battery-backed systems.
The DDPAK/TO-263-5 surface-mount package has a large exposed copper tab on the bottom that must be soldered to a PCB copper plane for thermal management — at 1.5A and 0.18V dropout the dissipation is only 0.27W, but the tab still carries the heat from the die. The enable pin allows the output to be shut down without removing the input voltage, useful for sequencing multiple rails or reducing standby power in a multi-regulator design.