1.8 V fixed rail for precision analog and sensor supplies
The Texas Instruments TPS73118MDBVREP is a 150 mA low-dropout linear regulator with a fixed 1.8 V output, packaged in a SOT-23-5 footprint. It delivers a clean, regulated rail for noise-sensitive loads like ADC references, sensor front-ends, and low-voltage digital cores that cannot tolerate the ripple from a switching converter. The 0.1 V maximum dropout at 150 mA means the input rail can sit as low as 1.9 V and still maintain regulation — useful when the supply is a battery near end-of-discharge or a lightly loaded 2.5 V bus. The 550 µA quiescent current and 750 µA max supply current keep the LDO's own draw low enough for always-on domains in battery-powered equipment.
PSRR profile and noise rejection across frequency
Power-supply rejection ratio is specified at 58 dB at 100 Hz, rolling off to 37 dB at 10 kHz. This means the LDO attenuates 100 Hz ripple — from a mains-derived rectifier or a 100 kHz switching converter's fundamental — by roughly 58 dB and 37 dB respectively. For a 10 mVpp ripple on the input at 1 kHz, less than 20 µVpp passes to the output, which is clean enough for a 12-bit ADC reference rail without additional post-filtering. The -55°C to 125°C operating temperature range covers military and industrial environments — avionics, downhole instrumentation, and engine-bay electronics where the ambient swings beyond commercial limits. The protection features — over-current, over-temperature, short-circuit, and reverse polarity — guard against fault conditions on the output or input without latching up or damaging the regulator.
SOT-23-5 footprint and board integration
The SOT-23-5 (SC-74A) package occupies roughly 3 mm × 3 mm on the board, with a 0.95 mm pin pitch. The enable pin (active-high) allows the regulator to be shut down to near-zero quiescent current for power gating in multi-rail systems. Surface-mount assembly with standard reflow profiles; no special handling beyond the usual MSL precautions for a plastic-encapsulated device.