LM317M

LM317M is a classic 3-terminal adjustable positive voltage regulator (LM317 family), typically in a TO-220 package. It holds a 1.25 V reference between output and adjust and uses external resistors to set the output voltage.
Key points:
- Pinout (front view, left to right): Adjust, Output, Input.
- Output range: adjustable from about 1.25 V up to ~37 V, depending on input voltage and dissipation.
- Current capability: up to ~1.5 A with adequate heat sinking.
- Input voltage: up to ~37–40 V; dropout around 2 V at moderate currents.
- Protection: built-in current limit and thermal shutdown.
- Stability: requires input and output capacitors for best transient response (e.g., 0.1 µF input, 1 µF+ output).
Use for simple, low-cost adjustable power supplies, lab benches, and battery chargers. It’s a linear regulator, so efficiency depends on voltage drop and heat sinking.

LM317M is part of the LM317 adjustable regulator family. Direct equivalents (same function) include:
- LM317 (standard)
- LM317T (TO-220)
- LM317L (low-current)
- LM317HV (high-voltage)
- LM350 (3 A adjustable, higher current)
Other vendors’ LM317-compatible parts may exist with different packaging suffixes. Always verify pinout and thermal/voltage specs for your chosen package, as some variants differ in pins or heat dissipation.

Here are the key features of the LM317M (3-terminal adjustable positive regulator):
- Output voltage adjustable from about 1.25 V to ~37 V (Vout = Vref(1+R2/R1) + Iadj·R2)
- Adjustable up to 1.5 A load current (with current limit)
- Input–output differential up to about 40 V
- Internal current limiting and thermal/shutdown protection; safe-area protection
- Requires only two external resistors to set the output
- Stable with external capacitors: typically 0.1 µF input cap; 1 µF (or larger) output cap; adjust-pin cap optional for ripple rejection
- Not a true low-dropout regulator; typically needs ~2 V headroom at full load
- Available in TO-220/M package variants; widely used for simple adjustable supplies
Note: Always place close, appropriate caps to ensure stability and transient response.

- Pin count: 3 pins.
- Function: Adjustable positive voltage regulator. Uses an external resistor divider to set the output. Vout ≈ Vref(1 + R2/R1) + Iadj·R2, with Vref ≈ 1.25 V; typical current up to ~1.5 A (depending on package/heat sinking); dropout around 2 V.
- Common TO-220 (front view): Pin 1 = ADJ, Pin 2 = OUT, Pin 3 = IN.

LM317M is manufactured by Texas Instruments (TI). TI is an American multinational technology company that designs and manufactures semiconductors, especially analog and embedded processing products.

LM317M is a 1.5 A adjustable positive linear regulator (TO-220/M) with input up to ~40 V, output 1.25–37 V, dropout ≈2 V (heat sinking required for higher power).
Common applications:
- Adjustable bench power supplies and general adjustable voltage regulation.
- Constant-current LED drivers (Iout ≈ 1.25 V / Rset).
- Post-regulation or simple pre-regulation in linear power supplies.
- Battery charging circuits and hobby projects needing a programmable regulator.
- Lab instrumentation and test circuits requiring a stable, adjustable reference/rail.
- Automotive/industrial rails where adequate cooling is available.

LM317M is the through-hole TO-220 package version (TO-220AB) of the LM317 adjustable regulator, with three leads and a metal tab.