The LP38690DTX-2.5/NOPB is an active-production Texas Instruments LDO regulator with a fixed 2.5V output and 1A current capability in the TO-252-3 (DPak) surface-mount package. Operating temperature spans -40°C to 125°C, covering both industrial floor and under-hood automotive ambient without derating concerns.
PSRR and quiescent current — what they mean for the rail
PSRR is 55 dB at 120 Hz — this is the ripple rejection from a full-wave rectified input. For a 5V rail with 100 mVpp of 120 Hz ripple, the output sees roughly 0.18 mVpp of that frequency component. Above a few hundred kHz the PSRR rolls off, so a ceramic output cap with low ESR is needed to keep high-frequency noise from coupling through. Quiescent current is 55 µA typical, with a maximum supply current of 100 µA across load and temperature.
Package and thermal — TO-252-3 layout notes
The tab must be soldered to a copper pad on the PCB for thermal dissipation — without it, the 1A output at high dropout will push the junction above the 125°C limit. A 1-inch-square copper pour on the bottom layer, connected with vias, keeps the junction temperature in check. The single regulator channel and fixed 2.5V output mean no external resistor divider is needed — the output voltage is set internally. The input cap and output cap are the only external components required for a basic application.