BETANominal reference1.25 V · OUT to ADJ
Adjustable linear regulator
LM317 Specifications
Review LM317 electrical specifications, operating conditions and package details.
Package view
Key specifications
The regulated quantity is the voltage between OUTPUT and ADJUST. The external divider determines the output relative to ground.
Adjustable output1.2–37 V · with adequate headroom
Operating junction0–125 °C · LM317 grade
Electrical connections3 ADJ · OUT · IN
Package details
LM317T · TO-220
| Property | Details |
|---|---|
| Manufacturer | STMicroelectronics |
| Part number | LM317T |
| Package | TO-220 |
| Connections | 3 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | T |
| Thermal reference | Cooling and mounting dependent; see DS0433 |
Operating characteristics
ST LM317 · not LM217 or LM317B
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Output adjustment | 1.2–37 V | Requires input headroom, load and suitable cooling |
| Reference voltage | 1.2 / 1.25 / 1.3 V | Minimum / typical / maximum; Table 4 conditions |
| Junction temperature | 0–125°C | Selected LM317 grade |
| Minimum load at 40 V differential | 3.5 mA typical; 10 mA maximum | Output may rise if the load is insufficient |
| Adjustment current | 50 µA typical; 100 µA maximum | Include its contribution through R2 |
No specifications match. Try a parameter name or a unit.
Base conditions: VIN − VOUT = 5 V, IOUT = 500 mA, IMAX = 1.5 A, PMAX = 20 W unless stated. These are test conditions, not a package dissipation guarantee.
Regulation and rejection
Manufacturer conditions retained
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Line regulation at 25°C | 0.01%/V typical; 0.04%/V maximum | VIN − VOUT = 3–40 V |
| Line regulation over temperature | 0.02%/V typical; 0.07%/V maximum | VIN − VOUT = 3–40 V |
| Load regulation, output ≤5 V | 5 mV typical; 25 mV maximum | 25°C; IOUT = 10 mA to IMAX |
| Ripple rejection without CADJ | 65 dB typical | 120 Hz; 25°C |
| Ripple rejection with CADJ | 66 dB minimum; 80 dB typical | CADJ = 10 µF; 120 Hz; 25°C |
No specifications match. Try a parameter name or a unit.
The adjustable output and test load affect which row applies; consult Table 4 for complete conditions.
A nominal 5 V supply
9 V input · 120 Ω / 360 Ω divider
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| R1 · OUTPUT to ADJUST | 120 Ω | Reference current ≈ 1.25 / 120 = 10.42 mA |
| R2 · ADJUST to GND | 360 Ω | Nominal resistor ratio 3:1 |
| Ideal output | 5.00 V | 1.25 × (1 + 360 / 120) |
| Including typical IADJ | 5.018 V | Adds 50 µA × 360 Ω = 18 mV |
| Input bypass | 0.1 µF | Place close to the input and return |
| Output capacitor | 1 µF tantalum | Illustrative transient improvement from manufacturer guidance |
No specifications match. Try a parameter name or a unit.
Use resistor and capacitor ratings appropriate to the circuit. The drawing omits optional adjustment bypass and its associated protection diode.
Headroom and thermal design
Current ratings require cooling
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Pass-stage estimate | PD ≈ (VIN − VOUT) × IOUT | Include divider current in IOUT |
| TO-220 RθJC | 5°C/W | Package reference; actual mounting matters |
| D²PAK RθJC | 3°C/W | Package reference; actual PCB copper matters |
| Overload protections | Current, thermal and safe-area protection | Do not use protection as normal regulation |
| High differential voltage | Available current decreases | See manufacturer curves and operating limits |
No specifications match. Try a parameter name or a unit.
The LM317 is a linear regulator: excess voltage is dissipated rather than efficiently converted.
Package and stress limits
LM317T · TO-220
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Connections | 1 ADJUST · 2 OUTPUT · 3 INPUT | Follow the selected package orientation |
| Tab / thermal pad | OUTPUT · pin 2 | Not GND |
| Input-to-output absolute maximum | 40 V | Stress rating; not a normal design target |
| Storage temperature | −65 to +150°C | Unpowered |
| Lead pitch | 2.54 mm | Verify the selected manufacturer drawing |
No specifications match. Try a parameter name or a unit.
The same three numbers have different functions from a 7805. Do not substitute without checking connections.
Connections by function
Select a pin for its function, connection guidance and electrical notes.