LM317T-DG

LM317T-DG is a TO-220 ordering code in STMicroelectronics' own LM317 system — an adjustable three-terminal positive linear regulator whose output is set from 1.2 V to 37 V by two external resistors, with internal current limiting, thermal overload protection and safe-area compensation. Read this page on the ST system, not on another maker's LM317: the -DG suffix is ST's own order-code variant denoting the dual-gauge heatsink version of the TO-220 tab, so the device is the ST LM317T electrically, with the heatsink tab specified by the DG variant — check the tab drawing at receiving inspection and do not silently substitute a standard-gauge code where the mechanical fit was qualified on DG. Adjustability is the procurement advantage: one part number covers any rail in the range, which simplifies spares for service, bench and low-volume industrial equipment. Selection advice: this is a standard linear regulator with roughly 2–3 V of dropout, not an LDO — it cannot make 3.3 V from a 5 V rail at load; and at 1.5 A-class currents with a large input-output differential the TO-220 must be heatsinked, with dissipation computed as (VIN − VOUT) × IOUT. For 0.5 A or 0.1 A rails the smaller LM317M and LM317L variants run cooler and cheaper. Parameters verified against STMicroelectronics documentation.