Adjustable LDO for post-rectifier analog rails
The LM1117S-ADJ is an adjustable positive LDO regulator from Texas Instruments, delivering up to 800 mA continuous output with a maximum dropout voltage of 1.2 V at that current. The single regulator output is positive configuration, with over-current and over-temperature protection built in.
Dropout and headroom planning
The 1.2 V maximum dropout at 800 mA sets the minimum input-to-output differential. The 5 mA quiescent current is moderate — acceptable for always-on rails where the load current dominates the power budget. Maximum input voltage is 15 V, and the supply current (including the pass-element drive) peaks at 10 mA.
The part is also marked RoHS non-compliant, which may restrict its use in new EU-market designs. Sourcing is limited to independent-distributor inventory — franchised stock is exhausted. For volume requirements or long-term production, the buyer should evaluate pin-compatible alternatives within the LM1117 family or consider a drop-in from another vendor. The TO-263-4 (D²Pak) footprint is widely second-sourced; several manufacturers offer adjustable LDOs in the same package with similar dropout and current ratings.
Package and mounting — D²Pak thermal considerations
The TO-263-4 (D²Pak) surface-mount package with three leads plus a tab requires a copper pad on the PCB for thermal dissipation. The tab's solder profile follows standard lead-free reflow for large-body packages; a thermocouple on the tab during profile validation is recommended.