Fixed 12V rail, 3A continuous — the TO-220-5 workhorse
The MIC29301-12WT is a fixed 12V output, 3A-capable positive LDO regulator from Micrel, housed in a through-hole TO-220-5 package. It delivers a regulated 12V rail from an input up to 26V, with a maximum dropout voltage of 0.6V at the full 3A load — meaning the input needs to stay above 12.6V to hold regulation under maximum current. The single-regulator design includes an Enable control pin and a comprehensive protection suite: over-current, over-temperature, reverse polarity, and transient voltage, which reduces the need for external clamp diodes on the supply side.
0.6V dropout at 3A — headroom planning
The 0.6V maximum dropout at 3A is the key number for BOM margin. If your input rail sags during brownout or cold-crank, the MIC29301-12WT holds regulation as long as the input stays above 12.6V. Below that, the output follows the input minus dropout — so a 12V rail at 3A needs a pre-regulator or bulk capacitor bank sized to keep the input above that threshold during transients. The 26V absolute maximum input gives comfortable headroom for 24V nominal supplies, but the dropout figure, not the max input, drives the minimum bus voltage design target.
Protection set — fewer external parts
Over-current, over-temperature, reverse polarity, and transient voltage protection are all integrated. For a 3A industrial rail, this typically eliminates a series Schottky for reverse-battery and an external current-limit resistor. The transient voltage protection handles short-duration spikes on the input line, but sustained overvoltage beyond 26V still needs an external TVS or upstream clamp. The Enable pin allows sequenced power-up or shutdown without a separate load switch.