150 mA LDO with 60 dB PSRR — the noise-rejection ceiling
The TPS76318QDBVRG4Q1 is a fixed 1.8 V output LDO from Texas Instruments, rated for 150 mA continuous output. The 60 dB PSRR at 1 kHz means it attenuates ripple from the upstream supply by a factor of 1000 — a switching regulator feeding this LDO will have its switching harmonics knocked down below the noise floor of a sensitive analog load. The enable pin lets a system controller sequence the 1.8 V rail on and off, useful for power-gating in body-control or infotainment modules.
Protection set and quiescent draw
Built-in over-current, over-temperature, and reverse polarity protection cover the common fault conditions on a vehicle power bus — a shorted load or a hot-swap transient won't take out the regulator. Quiescent current is 100 µA typical, with a maximum supply current of 140 µA, keeping the standby drain low enough for always-on modules that draw from the battery. The SOT-23-5 package (SC-74A,) occupies about 3 mm² of board area. The exposed pad on the SOT-23-5 variant is the thermal path — a via array under the pad to the ground plane pulls heat away from the die. For a 150 mA load with 3 V dropout, the power dissipation is 0.45 W; the junction-to-ambient thermal resistance of the SOT-23-5 is around 220°C/W, so the temperature rise is about 99°C above ambient — within the 125°C limit if the ambient stays below 26°C, or with airflow.