Fixed 2.5 V LDO for 1 A rails — what to watch
The Texas Instruments LP38690SDX-2.5 is a single-output positive LDO regulator delivering a fixed 2.5 V at up to 1 A. It comes in a 6-WSON (3x3 mm) exposed-pad package rated for junction temperatures from -40 to 125 °C, making it suitable for industrial and automotive-adjacent environments where the board sees under-hood or outdoor thermal cycling. The 55 dB PSRR at 120 Hz tells you it rejects line-frequency ripple well enough for post-switcher clean-up on analog or mixed-signal rails.
Dropout and headroom — the number that bites
Maximum dropout is 1.3 V at 1 A. The input rail must stay above 2.5 V + 1.3 V to maintain regulation at full load.
Thermal: the exposed pad is not optional
The 6-WSON package with exposed pad (3x3 mm footprint) relies on a good thermal via pattern to the ground plane. Without it, 1 A output at high dropout will push the junction past 125 °C. The protection features include over-temperature shutdown, but that is a last-resort guard, not a design margin. Plan the copper area under the pad as part of the layout review.
Lifecycle and compliance
The LP38690SDX-2.5 is listed as active with no end-of-life notification. Note the RoHS compliance status: this variant is marked RoHS non-compliant, so verify your assembly line's solder profile and exemption requirements before committing the BOM.