What this LDO is and where it fits
The Texas Instruments LP38691QSD-1.8/NOPB is a single-output, fixed 1.8 V positive linear regulator rated for 500 mA continuous output. It belongs to the Automotive, AEC-Q100 series, qualified for the -40°C to 125°C temperature range. The 55 dB PSRR at 120 Hz and 55 µA quiescent current make it a fit for noise-sensitive always-on rails in automotive ECUs, sensor modules, and infotainment controllers where a clean 1.8 V supply is needed for MCU core or analog front-end power.
500 mA output — what it means for the rail budget
The part is rated for 500 mA continuous output at 1.8 V fixed.
55 µA quiescent current and 55 dB PSRR
The 55 µA Iq and 55 dB PSRR at 120 Hz are the key specs for battery-backed or always-on modules.
Package and mounting
The 6-WSON (3x3 mm) package with exposed pad is a small, low-profile footprint — 3 mm on a side — that fits tight automotive PCBs. The exposed pad must be soldered to a thermal land on the board; without a via pattern under the pad, the part will hit thermal shutdown well before 500 mA at 125°C ambient. For rework, the WSON is manageable with hot air if you preheat the board and work the pad evenly — the part is small enough that a standard nozzle can cover it, but the exposed pad wicks heat fast.
Lifecycle and sourcing
The LP38691QSD-1.8/NOPB carries an Active lifecycle status from Texas Instruments. It is ROHS3 compliant. No last-time-buy notice is in effect, and the part is available for new designs and production.