LM317 voltage regulator: Pinout, CALCULATOR, and circuits

Do you need to build a variable DC power supply? It has a lot of choices for you. However, many people choose LM317 as the first, me too! Why?

Because It has high efficiency, is easy, and is cheaper.

It can replace 1.5 V or 9 V battery and others as we want to do.

Is it really? You find out below.

LM317 voltage regulator: Pinout, CALCULATOR and circuits

LM317 Datasheet

It is an adjustable 3-terminal positive voltage regulator, to supply more than 1.5 A of load current, and an output adjustable voltage: 1.2 V to 37 V range.

Also, LM317 has an internal current limiting, temperature detects shutdown and safe area compensation.

LM317 pinout

LM317 Pinout on TO-220


Figure 1: LM317 pinout on TO-220

Look:

LM317 pinout


Connection Diagram various LM317 Pinout

  • LM317T on TO-220: output 1.5 A
  • LM317L on TO-92: output 100 mA
  • LM317K on TO-3: output 1.5 A
  • LM317 on DPARK: output 1.5 A

Basic Features

  • Output current in excess of 1.5 A
  • Output-Adjustable between 1.2 V to 37 V
  • Internal Short-Circuit Current Limiting or Output is short-circuit protected
  • Internal Thermal Overload Protection or Current limit constant with temperature
  • Output-Transistor Safe Operating Area Compensation
  • TO-220 Package like 2SC1061 transistors.
  • There are 1% output voltage Durability
  • There are max. 0.01% / V line regulation(LM317), and 0.3% load regulation (LM117)
  • There are 80 dB ripple rejection
typical application of LM317


Figure 2 the basic circuit diagram

Basic circuit diagram

If the distance from the IC regulator and input voltage is too much. We should put Ci to reduce any noise.

Next, see the figure circuit. You not need to put Co. But You want a high-efficiency output. You should add It to keep lower an ripple.

As IAdj is controlled to less than 100 uA, the little error is unimportant in most uses.

The input voltage to the LM317 must be at least 1.5 V greater than the output voltage.

Learn more: IC Voltage Regulators Information

LM317 calculator

This calculator will work for most DC Voltage Regulators with a reference voltage (VREF) of 1.25. Typically, the program resistor (R1) is 240 ohms for the LM117, LM317, LM138, and LM150.

Some said Iadj is very low current.

So, we may reduce it down. To be shorter and easy.

Vout = 1.25 V x {1 + R2/ R1}

Which is better?

For example:
You use R1 = 270 ohms and R2 = 390 ohms. It causes output is 3.06 V

Is it easy? If you have voltages choice with most resistors. In local stores near you.

look at the list:

Output Voltage with R1 and R2 List

1.43V : R1 = 470Ω, R2 = 68Ω
1.47V : R1 = 470Ω, R2 = 82Ω
1.47V : R1 = 390Ω, R2 = 68Ω
1.51V : R1 = 330Ω, R2 = 68Ω
1.51V : R1 = 390Ω, R2 = 82Ω
1.52V : R1 = 470Ω, R2 = 100Ω
1.53V : R1 = 390Ω, R2 = 82Ω
1.56V : R1 = 330Ω, R2 = 82Ω
1.57V : R1 = 270Ω, R2 = 68Ω
1.57V : R1 = 470Ω, R2 = 120Ω
1.57V : R1 = 390Ω, R2 = 100Ω
1.59V : R1 = 390Ω, R2 = 100Ω
1.60V : R1 = 240Ω, R2 = 68Ω
1.63V : R1 = 330Ω, R2 = 100Ω
1.63V : R1 = 270Ω, R2 = 82Ω
1.64V : R1 = 390Ω, R2 = 120Ω
1.64V : R1 = 220Ω, R2 = 68Ω
1.65V : R1 = 470Ω, R2 = 150Ω
1.66V : R1 = 390Ω, R2 = 120Ω
1.68V : R1 = 240Ω, R2 = 82Ω
1.71V : R1 = 330Ω, R2 = 120Ω
1.71V : R1 = 270Ω, R2 = 100Ω
1.72V : R1 = 220Ω, R2 = 82Ω
1.72V : R1 = 180Ω, R2 = 68Ω
1.73V : R1 = 470Ω, R2 = 180Ω
1.73V : R1 = 390Ω, R2 = 150Ω
1.76V : R1 = 390Ω, R2 = 150Ω
1.77V : R1 = 240Ω, R2 = 100Ω
1.81V : R1 = 270Ω, R2 = 120Ω
1.82V : R1 = 150Ω, R2 = 68Ω
1.82V : R1 = 330Ω, R2 = 150Ω
1.82V : R1 = 180Ω, R2 = 82Ω
1.83V : R1 = 390Ω, R2 = 180Ω
1.84V : R1 = 470Ω, R2 = 220Ω
1.86V : R1 = 390Ω, R2 = 180Ω
1.88V : R1 = 240Ω, R2 = 120Ω
1.89V : R1 = 470Ω, R2 = 240Ω
1.93V : R1 = 330Ω, R2 = 180Ω
1.93V : R1 = 150Ω, R2 = 82Ω
1.94V : R1 = 270Ω, R2 = 150Ω
1.96V : R1 = 390Ω, R2 = 220Ω
1.97V : R1 = 470Ω, R2 = 270Ω
1.99V : R1 = 390Ω, R2 = 220Ω
2.02V : R1 = 390Ω, R2 = 240Ω
2.03V : R1 = 240Ω, R2 = 150Ω
2.06V : R1 = 390Ω, R2 = 240Ω
2.08V : R1 = 330Ω, R2 = 220Ω
2.10V : R1 = 220Ω, R2 = 150Ω
2.12V : R1 = 390Ω, R2 = 270Ω
2.13V : R1 = 470Ω, R2 = 330Ω
2.16V : R1 = 330Ω, R2 = 240Ω
2.16V : R1 = 390Ω, R2 = 270Ω
2.19V : R1 = 240Ω, R2 = 180Ω
2.23V : R1 = 470Ω, R2 = 390Ω
2.25V : R1 = 150Ω, R2 = 120Ω
2.27V : R1 = 270Ω, R2 = 220Ω
2.27V : R1 = 330Ω, R2 = 270Ω
2.29V : R1 = 470Ω, R2 = 390Ω
2.29V : R1 = 180Ω, R2 = 150Ω
2.31V : R1 = 390Ω, R2 = 330Ω
2.36V : R1 = 270Ω, R2 = 240Ω
2.37V : R1 = 390Ω, R2 = 330Ω
2.40V : R1 = 240Ω, R2 = 220Ω
2.44V : R1 = 390Ω, R2 = 390Ω
2.50V : R1 = 470Ω, R2 = 470Ω
2.57V : R1 = 390Ω, R2 = 390Ω
2.61V : R1 = 220Ω, R2 = 240Ω
2.65V : R1 = 330Ω, R2 = 390Ω
2.66V : R1 = 240Ω, R2 = 270Ω
2.73V : R1 = 330Ω, R2 = 390Ω
2.74V : R1 = 470Ω, R2 = 560Ω
2.75V : R1 = 150Ω, R2 = 180Ω
2.76V : R1 = 390Ω, R2 = 470Ω
2.78V : R1 = 270Ω, R2 = 330Ω
2.78V : R1 = 220Ω, R2 = 270Ω
2.84V : R1 = 390Ω, R2 = 470Ω
2.92V : R1 = 180Ω, R2 = 240Ω
2.96V : R1 = 270Ω, R2 = 390Ω
2.97V : R1 = 240Ω, R2 = 330Ω
3.03V : R1 = 330Ω, R2 = 470Ω
3.05V : R1 = 390Ω, R2 = 560Ω
3.06V : R1 = 270Ω, R2 = 390Ω
3.06V : R1 = 470Ω, R2 = 680Ω
3.08V : R1 = 150Ω, R2 = 220Ω
3.13V : R1 = 220Ω, R2 = 330Ω
3.14V : R1 = 390Ω, R2 = 560Ω
3.18V : R1 = 240Ω, R2 = 390Ω
3.25V : R1 = 150Ω, R2 = 240Ω
3.28V : R1 = 240Ω, R2 = 390Ω
3.35V : R1 = 220Ω, R2 = 390Ω
3.37V : R1 = 330Ω, R2 = 560Ω
3.43V : R1 = 270Ω, R2 = 470Ω
3.43V : R1 = 390Ω, R2 = 680Ω
3.43V : R1 = 470Ω, R2 = 820Ω
3.47V : R1 = 220Ω, R2 = 390Ω
3.50V : R1 = 150Ω, R2 = 270Ω
3.54V : R1 = 180Ω, R2 = 330Ω
3.55V : R1 = 390Ω, R2 = 680Ω
3.70V : R1 = 240Ω, R2 = 470Ω
3.82V : R1 = 180Ω, R2 = 390Ω
3.83V : R1 = 330Ω, R2 = 680Ω
3.84V : R1 = 270Ω, R2 = 560Ω
3.88V : R1 = 390Ω, R2 = 820Ω
3.91V : R1 = 470Ω, R2 = 1K
3.92V : R1 = 220Ω, R2 = 470Ω
3.96V : R1 = 180Ω, R2 = 390Ω
4.00V : R1 = 150Ω, R2 = 330Ω
4.02V : R1 = 390Ω, R2 = 820Ω
4.17V : R1 = 240Ω, R2 = 560Ω
4.33V : R1 = 150Ω, R2 = 390Ω
4.36V : R1 = 330Ω, R2 = 820Ω
4.40V : R1 = 270Ω, R2 = 680Ω
4.43V : R1 = 220Ω, R2 = 560Ω
4.44V : R1 = 470Ω, R2 = 1.2K
4.46V : R1 = 390Ω, R2 = 1K
4.50V : R1 = 150Ω, R2 = 390Ω
4.51V : R1 = 180Ω, R2 = 470Ω
4.63V : R1 = 390Ω, R2 = 1K
4.79V : R1 = 240Ω, R2 = 680Ω
5.04V : R1 = 330Ω, R2 = 1K
5.05V : R1 = 270Ω, R2 = 820Ω
5.10V : R1 = 390Ω, R2 = 1.2K
5.11V : R1 = 220Ω, R2 = 680Ω
5.14V : R1 = 180Ω, R2 = 560Ω
5.17V : R1 = 150Ω, R2 = 470Ω
5.24V : R1 = 470Ω, R2 = 1.5K
5.30V : R1 = 390Ω, R2 = 1.2K
5.52V : R1 = 240Ω, R2 = 820Ω
5.80V : R1 = 330Ω, R2 = 1.2K
5.88V : R1 = 270Ω, R2 = 1K
5.91V : R1 = 220Ω, R2 = 820Ω
5.92V : R1 = 150Ω, R2 = 560Ω
5.97V : R1 = 180Ω, R2 = 680Ω
6.04V : R1 = 470Ω, R2 = 1.8K
6.06V : R1 = 390Ω, R2 = 1.5K
6.32V : R1 = 390Ω, R2 = 1.5K
6.46V : R1 = 240Ω, R2 = 1K
6.81V : R1 = 270Ω, R2 = 1.2K
6.92V : R1 = 150Ω, R2 = 680Ω
6.93V : R1 = 330Ω, R2 = 1.5K
6.94V : R1 = 180Ω, R2 = 820Ω
7.02V : R1 = 390Ω, R2 = 1.8K
7.10V : R1 = 470Ω, R2 = 2.2K
7.33V : R1 = 390Ω, R2 = 1.8K
7.50V : R1 = 240Ω, R2 = 1.2K
8.07V : R1 = 330Ω, R2 = 1.8K
8.08V : R1 = 150Ω, R2 = 820Ω
8.19V : R1 = 270Ω, R2 = 1.5K
8.30V : R1 = 390Ω, R2 = 2.2K
8.43V : R1 = 470Ω, R2 = 2.7K
8.68V : R1 = 390Ω, R2 = 2.2K
9.06V : R1 = 240Ω, R2 = 1.5K
9.58V : R1 = 330Ω, R2 = 2.2K
9.77V : R1 = 220Ω, R2 = 1.5K
9.90V : R1 = 390Ω, R2 = 2.7K
10.03V : R1 = 470Ω, R2 = 3.3K
10.37V : R1 = 390Ω, R2 = 2.7K
10.63V : R1 = 240Ω, R2 = 1.8K
11.25V : R1 = 150Ω, R2 = 1.2K
11.44V : R1 = 270Ω, R2 = 2.2K
11.48V : R1 = 330Ω, R2 = 2.7K
11.67V : R1 = 180Ω, R2 = 1.5K
11.83V : R1 = 390Ω, R2 = 3.3K
12.40V : R1 = 390Ω, R2 = 3.3K
12.71V : R1 = 240Ω, R2 = 2.2K
13.75V : R1 = 330Ω, R2 = 3.3K
15.31V : R1 = 240Ω, R2 = 2.7K
16.25V : R1 = 150Ω, R2 = 1.8K
16.53V : R1 = 270Ω, R2 = 3.3K
16.59V : R1 = 220Ω, R2 = 2.7K
18.44V : R1 = 240Ω, R2 = 3.3K
19.58V : R1 = 150Ω, R2 = 2.2K
20.00V : R1 = 220Ω, R2 = 3.3K
23.75V : R1 = 150Ω, R2 = 2.7K
24.17V : R1 = 180Ω, R2 = 3.3K
28.75V : R1 = 150Ω, R2 = 3.3K

For example:

You need 4.5 volts from a 3 x AA 1.5V battery in a series. But you have no them.

How to do it?

You have only LM317 and a lot of resistors. Yes! you can use them instead.

Look at the list above, in 4.5V voltage. We can use R1 = 150Ω, R2 = 390Ω.

It is easy, right?

LM317 heat sink calculator

What is the size of the heat sink enough?

LM317 is always hot while working. Though it has an over-temperature cut-out mode. But we should not release it too hot. We always install the heat sink.

Someone ask me. What size heat sink should we use? LM317 has a maximum temperature of 50 °C/W  without a heat sink.

I found this site, good for using LM317 heat sink calculator.

The LM317 Heat sink, how big?

You can find the LM317 on Amazon here if you’re interested.

For example LM317 circuit

  1. First Variable DC Power Supply
    I built It as a first power supply. Though it is very old, we have still used them for more than 20 years. Why it is great like this?
  2. Linear Selector Power supply Regulator
    Easy to select the ouput voltage: 1.5V, 3V, 4.5V, 5V, 6V, 9V at 1.5A
  3. 30V Dual DC variable power supply
    High voltage 0V to 60 volts at 1.5A and starts voltage at zero! good job.
  4. Great DC power supply
    High quality, 3A adjustable voltage regulator. Using LM317 and 2N3055 so easy and cheap. Adjust voltage in steps 3V, 6V, 9V, 12V. And In fine, 1.25V to 20V.
  5. 4 Lead Acid Battery charger circuits
    See 4 LM317 Lead-acid battery charger circuits for 6V, 12V, and 24V battery. With automatic charging and full charged Indicator using TL431. Easy to build.
  6. Dual power supply 3V,5V,6V,9V,12,15V
    Dual power supply circuit,can select voltage levels 3V,5V,6V,9V,12,15V at 1A and -3V,-5V,-6V,-9V,-12V,-15V at 1A, use LM317 (positive) LM337(negative) […]
  7. USB Battery Replacement
    This is a USB 5V to 1.5V Step-Down Converter Circuit. When we use a Cheap MP3 Player which uses only one 1.5V AA battery as its power supply.
  8. Low dropout 5v regulator
    This is 5V low dropout regulator circuit using a transistor and LED only so easy,lowest voltage input is 6V so across it is 1V only, make output is 5V 0.5A
  9. Gel cell battery charger circuit
    It can charge any size of the Gel cell batteries and extend the life of the Gel Cell battery. While the circuit is running, the LED indicates charging.
  10. Nicad Battery Charger using LM317T
    Here are Universal NiCd and NiMH battery charger circuit. It uses IC LM317T ( Hot IC) Control Current less 300mA, Size battery 2.4V,4.8V,9.6V. Low-cost circuit

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10 Comments

  1. worku

    Thank’s & GBU this EC member .

  2. vishal

    sir i want 5v,2a power supply circuit with calculation from 230

  3. sunday owen

    pleasr can this idea be used to build solar charge controller?

  4. Pls suggest any simple circuit which supplies output of +12V , -12V dual output with current rating of 1A
    I/p supply is +24V DC .

  5. CHRISTOPHER SILWAMBA

    IAM LEANING A LOT I THANK VERY MUCH OUT OF THE MANY THINGS U ARE REVIEWING.

  6. Abiodun Ogundipe

    Dear Sir/Ma

    We are spare part supplier in Nigeria,
    Company name with address
    DE- ACCORD SYNERGY CONCEPT NIG LIMiTED. NO6, Oba Amusa Avenue Sumbol Bus Stop, Lagos Nigeria.

    Kindly quote us for the bellow items for our customer.

    LM78S40    (Universal Switching Regulator) 2nos

    LM7805      (Voltage Regulator) 2nos

    Your best price and delivery

    Best Regards

    Abiodun Ogundipe

    +23435766398

  7. KUMERASAN

    sir i want a simple voltage regulator for increasing and decreasing the small halogen bulb
    input voltage is 12v AC and out put 6v dc with variable pot using matal cap transistor like LM317K.

    • Hello, Kumerasan
      Thanks for visiting.

      It is a good idea. Let me give you a comment. What is the small halogen rate, current or watts? Here is 5watts https://amzn.to/2XTskJm
      It uses current about 5W/6V = 0.8A. Yes, you can use LM317. It may very heat. But if you use 10W. It will use current more = 10w/6V = 1.6A.

      You cannot use alone LM317. You may use it with a power transistor. Or use LM350. It is easy, too. https://www.eleccircuit.com/lm350-adjustable-voltage-regulator/

      I hope this can help you.

      Ps. I also had the idea of using hydrogen tubes for my chickens.

      Do have chickens?

  8. m0n0

    It’s difficult to understand those sentences without grammatic and ortographic sense…

    • Hello m0n0,
      Thanks for your opinion. I will try to improve my English. I hope you will read this article again.

      Thanks a lot again my friends.

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