Fixed 12 V rail — dropout and thermal budget
The MIC2940A-12WU: Output is fixed at 12 V with a single regulator — no external resistor divider or adjust pin, which simplifies the BOM and eliminates a feedback-node noise path. At lower currents the dropout drops proportionally, but the 0.6 V ceiling governs the headroom budget. Without adequate pad area, the junction temperature will exceed the 125°C absolute maximum at full current in a 25°C ambient.
Protection and quiescent draw
Built-in over-current, over-temperature, and reverse-polarity protection means the regulator survives output shorts, thermal runaway, and a swapped supply connection without external clamp diodes or crowbar circuits. Quiescent current is 500 µA typical — for always-on rails in battery-backed or standby systems, this draw is low enough to avoid a separate low-Iq LDO for the keep-alive supply. Maximum supply current is 70 mA — this is the regulator's own consumption under fault or start-up conditions, not the load current. The 1.25 A output rating is the load capacity.
Temperature grade and package fit
An engine-bay ECU or outdoor industrial controller that sees 105°C ambient still has 20°C of junction margin before the thermal shutdown trips. The TO-263-3 (D2PAK) surface-mount package has three leads plus the exposed tab, which is the thermal path. The tab is electrically connected to the output — the PCB copper pour must be isolated from other nets unless the output rail can share the plane. Shipping in Tube format — not tape-and-reel — so the pick-and-place feeder setup differs from reel-fed parts. Confirm the tube-to-reel transfer with your CM if the line is set up for tape.