Fixed 2.5 V rail from a 12 V input — the dropout tells you the headroom
The ADP3309ARTZ-2.5RL7 is a single-output positive LDO from the anyCAP® family, delivering a fixed 2.5 V at up to 100 mA. Maximum input is 12 V, and the dropout voltage is 0.25 V at full load — that 250 mV of headroom between input and output is the floor; if your 2.5 V rail dips below regulation, the input rail is too close to 2.75 V under load.
Quiescent current and shutdown — what the 300 µA Iq means on a battery
Quiescent current is 300 µA typical, with a maximum supply draw of 2 mA. On a 100 mA output that is negligible, but in a battery-powered sensor that sleeps most of the time the 300 µA floor adds up — the shutdown pin (Control Features: Error Flag, Shutdown) drops Iq to near zero when the rail is not needed. Protection is limited to over-temperature shutdown; there is no over-current foldback or reverse-current blocking. The load itself must limit fault current, or the die temperature trip handles it indirectly.
SOT-23-5 footprint — board integration notes
Packaged in an SC-74A / SOT-753 (SOT-23-5) with a surface-mount footprint. The 0.95 mm pitch and 2.9 mm body length fit a standard 5-pin SOT-23 land pattern — no exotic stencil or pad geometry needed. Operating temperature range is -20°C to 80°C ambient, not the wider -40 to 125°C industrial band. For an outdoor or under-hood design this is a restriction — the part is suited to indoor or climate-controlled enclosures.