LM317AMDTX/NOPB - 1.5A Adjustable Linear Regulator, TO-252 | Texas Instruments
Référence : LM317AMDTX/NOPB ✓ ActifLM317AMDTX/NOPB Présentation
An adjustable linear regulator (often called a three-terminal regulator) maintains a stable output voltage set by an external resistor divider, while dissipating the difference between input and output voltage as heat. These regulators form the simplest building block in the power-management hierarchy: linear regulator -> voltage regulator -> power management IC -> semiconductor. They trade efficiency for low noise, simplicity, and low cost versus switching converters, and are ideal when a few watts of dissipation are acceptable and noise-sensitive analog or digital loads must share a clean rail.
Key electrical characteristics include a 4.2 V to 40 V input range, 1.25 V to 37 V adjustable output, typical 1.5 A load current with peak capability exceeding 1.5 A, line regulation of 0.01%/V (typical), and load regulation of 0.1% (typical). Internal protection covers thermal-overload, short-circuit current foldback, and safe-operating-area compensation. The DPAK (TO-252) tab serves as the heatsink, allowing moderate dissipation directly into PCB copper without a discrete heatsink.
Typical applications include local post-regulation after a switching converter, bench power supplies, battery chargers, LED current regulators, and industrial 24 V bus regulation. It is commonly used as a precision current source by setting R1 between VOUT and ADJ to program a constant 1.25 V across the sense resistor.
When designing with the LM317AMDTX/NOPB, an input bypass capacitor is recommended if the regulator is more than 6 inches from the filter capacitor of the supply, and an output capacitor (tantalum or low-ESR aluminum) improves transient response. Calculate worst-case power dissipation as (VIN(max) - VOUT(min)) x IOUT(max) and ensure the copper area on the tab keeps junction temperature below 125 C.
This page synthesizes distributor pricing, same-brand drop-in alternatives, cross-brand equivalents, and practical design notes not found in the manufacturer datasheet.
Alternatives de remplacement direct pour LM317AMDTX/NOPB — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
LM317AMDT/NOPB
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
LM317AEMP/NOPB
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
LM317AEMPX/NOPB
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
LM317MABDTG
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
LM317MBDTG
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
LM317MABDTRKG
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
LM317AMDTX/NOPB Valeurs maximales et caractéristiques électriques
| Topologie | Linear (LDO family, three-terminal adjustable) |
| Polarity | Positive adjustable |
| Input Voltage Range (max) | 4.2 V to 40 V |
| Plage de tension de sortie | 1.25 V to 37 V (adjustable) |
| Courant de sortie (max.) | 1.5 A |
| Output Voltage Accuracy | 1% (LM317A grade) |
| Line Regulation (typ) | 0.01 %/V |
| Load Regulation (typ) | 0.1 % |
| Reference Voltage (VREF) | 1.25 V typical (between VOUT and ADJ) |
| Température de jonction en fonctionnement | -40 C to +125 C |
| Boîtier | TO-252-3 (DPAK, 3 leads + tab) |
| Type de montage | Surface Mount |
| Lead-Free / RoHS | Yes (NOPB finish), RoHS compliant |
| Protection Features | Current limit, thermal shutdown, safe-area compensation |
| Packaging | Tape & Reel (suffix TX) |
Configuration des broches de LM317AMDTX/NOPB
| Broche 1 | ADJ — Adjust pin - sets VOUT via external resistor divider (VREF = 1.25 V typical) |
| Broche 2 | OUTPUT — Regulated output voltage; also tied to metal tab for heatsinking |
| Broche 3 | INPUT — Unregulated input supply (4.2 V to 40 V) |
Applications typiques
LM317AMDTX/NOPB convient pour 6 applications: Adjustable Bench Power Supply, LED Constant-Current Driver, Industrial 24V Bus Post-Regulator, Battery Charger Float Regulator, Audio Amplifier Pre-Regulator, Microcontroller Board Auxiliary Rail.
Adjustable Bench Power Supply
The LM317AMDTX/NOPB is a textbook regulator for hobby and lab bench supplies. The 1.25 V to 37 V adjustable output and 1.5 A continuous current cover virtually any analog rail a maker needs. Set VOUT via a 240 ohm R1 and a 5 kohm potentiometer as R2; the part's 1% accuracy means meter trim is rarely needed. Place input/output capacitors per datasheet, and bolt the tab to a small TO-220-style clip-on heatsink for currents above 0.5 A to keep junction temperature below 125 C.
Recommandé
LED Constant-Current Driver
A single resistor between VOUT and ADJ programs a constant 1.25 V across the sense resistor, turning the LM317AMDTX/NOPB into a stable 1.5 A current source for high-brightness LEDs. This topology outperforms resistor-only LED current limiting because regulation is independent of LED forward voltage drift. According to TI, choose R = 1.25 V / ILED - for example, 1.25 ohm at 1 A. The TO-252 tab provides ample copper-area heatsinking for 5 W to 10 W string dissipation.
Recommandé
Industrial 24V Bus Post-Regulator
Factory automation backplanes and PLCs often distribute a raw 24 V DC bus, but downstream analog and digital ICs need clean 5 V, 12 V, or 15 V rails. The LM317AMDTX/NOPB drops the 24 V bus to any value between 1.25 V and 22 V at up to 1.5 A. Its 40 V absolute-max input handles the 24 V plus transient surges defined in IEC 61131-2. According to TI, the part's 0.01 %/V line regulation keeps the output stable even as the bus droops under heavy stepper or solenoid load.
Recommandé
Battery Charger Float Regulator
Float-charging sealed lead-acid (SLA) or lithium chemistries benefits from the LM317AMDTX/NOPB's constant-voltage, current-limited behavior. Set VOUT to 13.8 V for a 12 V SLA string, and add a series resistor at the output to program the bulk charge current. The TO-252 package dissipates the input-to-output differential cleanly through the tab and into PCB copper. According to TI, internal thermal shutdown protects the part if the charger is shorted or operated above 40 V input.
Recommandé
Audio Amplifier Pre-Regulator
Linear pre-regulation before a Class-D amplifier or op-amp output stage reduces switching noise and hum that would otherwise couple into the audio path. The LM317AMDTX/NOPB delivers quiet, ripple-free rails at +/-15 V (using the LM337 negative complement) for op-amp supplies, or a single 5 V to 12 V rail for Class-D front-end stages. The part's 1% accuracy translates directly into lower THD+N because supply rejection improves with regulated voltage precision. The TO-252 tab serves as the only required heatsink below 1 A.
Recommandé
Microcontroller Board Auxiliary Rail
Many MCU development boards (Arduino shields, ESP32 breakout boards, custom STM32 designs) accept a wide 7 V to 24 V DC input but need clean 5 V or 3.3 V rails for sensors and peripherals. The LM317AMDTX/NOPB is a robust post-regulator after a switching pre-converter, lowering EMI in the analog sections. Its 1.5 A capability is more than enough for sensor stacks, displays, and a small MCU simultaneously. According to TI, the enable-free design (always-on when VIN present) simplifies drop-in use behind a downstream buck regulator.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour LM317AMDTX/NOPB — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | LM317AMDT/NOPB | LM317AEMP/NOPB | LM317MABDTG | LM317MBDTG | LM317MABDTRKG |
|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | onsemi | onsemi | onsemi |
| Package | TO-252-3 (DPAK) | TO-252-3 (DPAK) - same | SOT-223-4 - same | TO-252-3 (DPAK) - same | TO-252-3 (DPAK) - same | TO-252-3 (DPAK) - same |
| Output Current (max) | 1.5 A | 1.5 A | 1.5 A | 1.5 A | 1.5 A | 1.5 A |
| Input Voltage Range | 4.2 V to 40 V | 4.2 V to 40 V | 4.2 V to 40 V | 4.2 V to 40 V | 4.2 V to 40 V | 4.2 V to 40 V |
| Output Voltage Range | 1.25 V to 37 V | 1.25 V to 37 V | 1.25 V to 37 V | 1.25 V to 37 V | 1.25 V to 37 V | 1.25 V to 37 V |
| Output Voltage Accuracy | 1% (A grade) | 1% (A grade) | 1% (A grade) | 1% (A grade) | 4% (standard grade) | 1% (A grade) |
| Lead-Free / RoHS | Yes (NOPB), RoHS | Yes (NOPB), RoHS | Yes (NOPB), RoHS | Yes, RoHS | Yes, RoHS | Yes, RoHS |
| Packaging Form | Tape & Reel (2,500) | Tube | Tube | Tube | Tube | Tape & Reel (2,500) |
Principaux différenciateurs
- 1% output accuracy (A grade) versus standard LM317's 4% (vs LM317MBDTG (standard grade))
- Tape-and-reel packaging for high-volume SMT lines (vs LM317AMDT/NOPB (tube))
- Wider 4.2 V to 40 V input range versus LDOs like LM1117 (vs LM1117MPX-1.8)
Notes de conception
Estimated: at VIN = 24 V, VOUT = 12 V, IOUT = 1 A, the LM317AMDTX/NOPB dissipates (24 - 12) x 1 = 12 W. The DPAK (TO-252) tab is the only heatsink; solder it to at least 1 square inch of 2 oz copper on the PCB and verify theta_JA from the datasheet thermal table. At 12 W the part will reach thermal shutdown without adequate copper; reduce VIN/VOUT differential or add a clip-on TO-220 heatsink bolted to the tab.
According to TI, place a 0.1 uF ceramic bypass capacitor directly at the INPUT pin (within 0.25 inch) if the regulator is more than 6 inches from the bulk filter capacitor. Add a 1 uF to 10 uF tantalum or low-ESR aluminum on OUTPUT to improve transient response. The OUTPUT tab is electrically hot, so keep the copper-pour clearance to ground planes at the manufacturer's recommended minimum (typically 0.5 mm to 1 mm).
Do not program VOUT below 1.25 V - the internal reference sets the floor. Floating the ADJ pin (no resistors) puts the part into an undefined state where VOUT rises to near VIN; always populate R1 from OUTPUT to ADJ (typically 240 ohm) before applying power. Do not exceed 40 V on INPUT even briefly - the internal pass transistor will avalanche. When using as a current source, never open-circuit the ADJ-to-OUTPUT sense resistor or the part will drive VOUT to VIN and destroy downstream loads.
Informations de conformité
Lead-free (NOPB) per DigiKey and TI product page; RoHS compliant. AEC-Q100 status is not qualified - for automotive designs choose an AEC-Q100 qualified part from the same family (e.g., LM317A-Q1 variants). Halogen-free status not stated in verified web data and marked unknown.
