apogeeweb title
Home  Technical Articles   LM317 Voltage Regulator: Alternative, Datasheet, Applications [Video]

Nov 19 2020

LM317 Voltage Regulator: Alternative, Datasheet, Applications [Video]


LM317 is a adjustable 3-terminal positive-voltage regulator, this bolg covers LM317 regulator alternative, datasheet, applications, features and other information on how to use and where to use this device.

A Basic Introduction to LM317 Voltage Regulator



LM317 Pinout

LM317 Features

LM317 Applications

LM317 Circuit

LM317 Parameters

LM317 CAD Model

LM317 Advantage

LM317 Electrical Characteristics

LM317 Package

LM317 Alternatives

LM317 Equivalents

Where to use LM317

How to use LM317

LM317 Manufacturer

Component Datasheet


LM317 Pinout

lm317 pinout


Pin Number Pin Name Description
1 Adjust This pins adjusts the output voltage
2 Output Voltage (Vout) The regulated output voltage set by the adjust pin can be obtained from this pin
3 Input Voltage (Vin) The input voltage which has to be regulated is given to this pin

LM317 Features

• Output voltage range adjustable from 1.25 V to 37 V

• Output current greater than 1.5 A

• Internal short-circuit current limiting

• Thermal overload protection

• Output safe-area compensation

LM317 Applications

• ATCA solutions

• DLP: 3D biometrics, hyperspectral imaging, optical networking, and spectroscopy

• DVR and DVS

• Desktop PCs

• Digital signage and still cameras

• ECG electrocardiograms

• EV HEV chargers: levels 1, 2, and 3

• Electronic shelf labels

• Energy harvesting

• Ethernet switches

• Femto base stations

• Fingerprint and iris biometrics

• HVAC: heating, ventilating, and air conditioning

• High-speed data acquisition and generation

• Hydraulic valves

• IP phones: wired and wireless

• Intelligent occupancy sensing

• Motor controls: brushed DC, brushless DC, lowvoltage, permanent magnet, and stepper motors

• Point-to-point microwave backhauls

• Power bank solutions

• Power line communication modems

• Power over ethernet (PoE)

• Power quality meters

• Power substation controls

• Private branch exchanges (PBX)

• Programmable logic controllers

• RFID readers

• Refrigerators

• Signal or waveform generators

• Software-defined radios (SDR)

• Washing machines: high-end and low-end

• X-rays: baggage scanners, medical, and dental

LM317 Circuit

lm317 circuit

LM317 Parameters

Output options

Adjustable Output

Iout (Max) (A)


Vin (Max) (V)


Vin (Min) (V)


Vout (Max) (V)


Vout (Min) (V)


Noise (uVrms)


Iq (Typ) (mA)


Thermal resistance θJA (°C/W)


Approx. price (US$)

1ku | 0.14

Load capacitance (Min) (µF)




Regulated outputs (#)



Accuracy (%)


PSRR @ 100 KHz (dB)


Dropout voltage (Vdo) (Typ) (mV)


Operating temperature range (C)

0 to 125

Ihs Manufacturer


Brand Name

Texas Instruments

LM317 CAD Model

Package Pins Download
DDPAK/TO-263 (KTT) 3 View options
SOT-223 (DCY) 4 View options
TO-220 (KCS) 3 View options
TO-220 (KCT)
3 View options

LM317 Electrical Characteristics

Over recommended ranges of operating vitual junction temperature (unless otherwise noted)

LM317 Package

  • DDPAK/TO-263 (KTT)

lm317 package

  • SOT-223 (DCY)

lm317 package

  • TO-220 (KCS)

lm317 package

  • TO-220 (KCT)

lm317 package

LM317 Alternatives

Share the same functionality and pinout but is not an equivalent to the compared device:

LM7805, LM7806, LM7809, LM7812, LM7905, LM7912, LM117V33, XC6206P332MR.

LM317 Equivalents

LT1086, LM1117 (SMD), PB137, LM337 (Negative Variable Voltage regulator)

Where to use LM317

When it comes to variable voltage regulation requirements LM317 would most likely be the first choice. Apart from using it as a variable voltage regulator, it can also be used as a fixed voltage regulator, current limiter, Battery charger, AC voltage regulator and even as an adjustable current regulator. One notable drawback of this IC is that it has a voltage drop of about 2.5 across it during regulation, so if you looking to avoid that problem look into the other equivalent IC’s given above.

So, if you are looking for a variable voltage regulator to deliver current up to 1.5A then this regulator IC might be the right choice for your application.

How to use LM317

LM317 is a 3-terminal regulator IC and it is very simple to use. It has many application circuits in its datasheet, but this IC is known for being used as a variable voltage regulator. So, let’s look into how to use this IC as a variable voltage regulator.

As said earlier the IC has 3 pins, in which the input voltage is supplied to pin3 (VIN) then using a pair of resistors (potential divider) we set a voltage at pin 1 (Adjust) which will decide the output voltage of the IC that is given out at pin 2 (VOUT). Now to make it act as a variable voltage regulator we have to set variable voltages at pin 1 which can be done by using a potentiometer in the potential divider. The below circuit is designed to take 12V (you can supply up to 24V) as input and regulate it from 1.25V to 10V.

lm317 circuit

The Resistor R1 (1K) and the potentiometer (10k) together creates a potential difference at adjust pin which regulates the output pin accordingly. The formulae to calculate the Output voltage based on the value of resistors is

VOUT = 1.25 × (1 + (R2/R1))

Now, let’s verify this formula for the above circuit. The value of R1 is 1000 ohms and the value of R2 (potentiometer) is 5000 because it is a 10k potentiometer placed at 50% (50/100 of 1000 is 5000).

Vout  = 1.25 × (1 + (5000/1000))

          = 1.25 × 6

          = 7.5V

And the simulation shows 7.7 V which is pretty much close. You can vary the output voltage by simply varying the potentiometer. In our circuit, a motor is connected as a load which consumes around 650mA you can connect any load up to 1.5A.

The same formulae can also be used to calculate the value of resistor for you required output voltage. One easy way to do this is to use this online calculator to randomly substitute the value of resistors you have and check which output voltage you will get.

LM317 Manufacturer

Texas Instruments Inc. (TI)  is an American technology company that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globally. Its headquarters are in Dallas, Texas, United States. TI is one of the top ten semiconductor companies worldwide, based on sales volume. Texas Instruments's focus is on developing analog chips and embedded processors, which accounts for more than 80% of their revenue. TI also produces TI digital light processing (DLP) technology and education technology products including calculators, microcontrollers and multi-core processors. To date, TI has more than 43,000 patents worldwide.

Component Datasheet

LM317 Datasheet


  • What is lm317 used for?

The LM317 serves a wide variety of applications including local, on card regulation. This device can also be used to make a programmable output regulator, or by connecting a fixed resistor between the adjustment and output, the LM317 can be used as a precision current regulator.

  • What is the maximum input voltage of lm317?

The LM317 is an adjustable voltage linear regulator that can output 1.25 – 37V at up to 1.5A current with an input voltage range of 3 – 40V.

  • What is the difference between lm317 and lm317t?

Member. There is no functional difference as they are one in the same. The T at the end just indicates that it's in a TO-220 package. They usually tag on extra things after the part name to reference things like package, temp range, etc.

  • Is lm317 a transistor?

The LM317 is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 32 V. ... By using a heat-sinked pass transistor such as a 2N3055 (Q1) we can produce several amps of current far above the 1.5 amps of the LM317.

  • How does an lm317 work?

The circuit consists of a low-side resistor and high-side resistor connected in series forming a resistive voltage divider which is a passive linear circuit used to produce an output voltage which is a fraction of its input voltage. 

  • What is IC lm317?

The LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 37 V. It requires only two external resistors to set the output voltage. The device features a typical line regulation of 0.01% and typical load regulation of 0.1%.

  • How do I know if my lm317 is working?

Testing lm317t.
If you look to the ic, the legs towards you, the right one is the input pin. you must see a difference of minimum 1.2V between the two pins, otherwise the IC is faulty. furthermore, the first test is to see if you have input voltage !

  • What is the working priciple of lm317?

LM 317 works on a very simple principle. It is a variable voltage regulator i.e. supports different output voltage levels for a constant applied input voltage supply.

  • How to make a simple voltage regulator circuit using LM317?


Related Articles

  • LM317 Circuit: Variable Low Power Regulated Power Supply
    I DescriptionAs we all know, low-power regulated power supplies are widely used electronic equipment in electronic system testing. However, this low-power power supply still has some inconvenience to ...
  • LM317 Typical Application Circuit
    IntroductionThe LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 37V. In addition, it has the adva...
  • LM317 Voltage Regulator: Principle, Application [FAQ]
    DescriptionThis blog briefly introduces LM317 in two parts. The first part is the principle of the LM317 three-terminal adjustable voltage regulator; the second part is three application circuits with...
  • LM317: Switched Mode Power Supply
    IntroductionA switched-mode power supply (SMPS) is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. Switched mode power supplies have replace...

0 comment

Leave a Reply

Your email address will not be published.