Adjustable LDO for moderate-current analog rails
Its output can be set from 1.25 V up to 13.8 V using an external resistor divider, making it a flexible post-regulator for 3.3 V MCU rails, 1.8 V DDR termination, or analog supply lines that need clean, low-noise power.
Maximum dropout voltage is 1.2 V at the full 800 mA load. That means the input rail must be at least 1.2 V above the programmed output voltage across the full load and temperature range. For a 3.3 V output, plan on a 4.5 V or higher input bus to guarantee regulation at high temperature. This is not an ultra-low-Iq part — it is not the right choice for battery-powered always-on circuits. It is sized for line-powered or moderate-load applications where the 5 mA Iq is a small fraction of the 800 mA load. On-chip protection includes over-current and over-temperature shutdown. The over-temperature trip protects the die during a sustained short or high ambient; the over-current limit folds back the output. No reverse-current protection is listed — if the output can be forced above the input, an external Schottky diode across the regulator is standard practice.
SOT-223-4 footprint and thermal reality
For 800 mA at high dropout, the copper area on the PCB under the tab sets the junction temperature. A 1-inch-square copper pour on the top layer, with vias to an inner ground plane, keeps the junction below 125°C at 25°C ambient.
For dual-sourcing resilience, the closest functional peer is the LM1117IMPX-ADJNOPB (note the missing slash), which shares the same LM1117 core, 800 mA rating, and SOT-223 package. The only listed difference is a PSRR of 73 dB at 120 Hz versus 75 dB — a 2 dB delta that is negligible for most applications. Confirm the exact order code string for your BOM line.