Adjustable 1.5A positive regulator in SOT-223-4
The Texas Instruments LM317EMPX/NOPB is a three-terminal adjustable positive voltage regulator delivering up to 1.5A output current from a 37V maximum input rail. Output voltage is set by two external resistors from a 1.25V reference to 37V, covering the classic LM317 application space in a surface-mount SOT-223-4 package. The 80dB to 65dB PSRR at 120Hz makes it suitable for post-rectifier filtering in linear supplies where ripple rejection matters.
The adjustable output from 1.25V to 37V covers common analog rails (1.8V, 2.5V, 3.3V, 5V, 12V) with a single BOM line item. The 1.5A current rating is continuous at the output — derate above room temperature per the SOT-223-4 thermal resistance. PSRR of 80dB at 120Hz drops to 65dB at the same frequency under load; this is typical for a three-terminal regulator and adequate for most bench supplies and audio pre-regulators, though a post-regulator LDO may be needed for sensitive ADC references.
On-chip protection includes over-current limiting, thermal shutdown, and short-circuit current foldback — no external clamp diodes needed for most loads. The 0°C to 125°C operating junction range is commercial grade; the device is not rated for -40°C cold start or extended automotive under-hood use. The SOT-223-4 footprint with a large copper pad on the PCB improves heat spreading for sustained 1.5A operation.
The LM317 family has been in continuous production for decades, and this SOT-223-4 variant is a current catalog item. No official successor or second-source cross-reference is carried in the listing, though the LM317 pinout is industry-standard and multiple manufacturers offer functionally identical parts in the same package.