Tuesday, July 26, 2016

LM317

The LM317 is a popular adjustable linear voltage regulator. It was designed by Robert C Dobkin in 1976 while he worked at National Semiconductor.





SCHEMATIC DIAGRAM and PIN CONFIFURATION






OPERATION

As linear regulators, the LM317 and LM337 are used in DC to DC converter applications.
Linear regulators inherently waste as much current as they supply. When this current is multiplied by the voltage difference between input and output, a significant amount of heat results. Therefore the use of an LM317 commonly also requires a heat sink. For large voltage differences, the energy lost as heat can ultimately be greater than that provided to the circuit. This is the trade-off for using linear regulators which are a simple way to provide a stable voltage with few additional components. The alternative is to use a switching voltage regulator which is usually more efficient but has a larger footprint and requires a larger number of associated components.
In packages with a heat-dissipating mounting tab, such as TO-220, the tab is connected internally to the output pin which may make it necessary to electrically isolate the tab or the heat sink from other parts of the application circuit. Failure to do this may cause the circuit to short.




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32 comments:

  1. Anonymous26 July 2016 at 23:45

    that 5 voltage regulator can regulate my 220 volts ac?

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    Replies
    1. Arczed27 July 2016 at 00:42

      Yes since this IC is used in Power Supplies, it can definitely regulate the 220V AC :)

      Delete
  2. Unknown27 July 2016 at 00:40

    Hi Ma'am Ehm! According to your blog LM317 requires a heat sink .. What if I don't have a heat sink? Does it mean I cannot use my LM317? Or there is an alternative way or component I can use to replace heat sink?

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    Replies
    1. Arczed27 July 2016 at 00:53

      Hello Mam Christine! An LM317 can safely be used to dissipate up to 0.25 Watts without any external heatsinking. For example, an LED powered by a 9V battery, the 0.171 Watts of heat dissipated would not require a heatsink. Therefore you can still use the IC. However, if the total current requirement would be 0.15A and so the heat dissipated in the regulator would be 0.855 Watts. A heatsink would definitely be required or else the regulator would overheat. And by the way, there is no other component that can replace a heatsink :)

      Delete
  3. Unknown27 July 2016 at 04:05

    Yan po ba yung may A,O,I mam ehm.....

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    Replies
    1. Arczed27 July 2016 at 16:32

      Yes, so as you can see on the picture shown, the pin arrangement is Adjust, Vout and Vin.

      Delete
  4. Unknown30 July 2016 at 17:34

    This comment has been removed by the author.

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  5. Unknown30 July 2016 at 17:36

    Why in our circuit board for power supply, we combined the Vin and Vout in a same path? Can you tell us why and what will happen? Sorry but I just can't understand even though I listened to what Sir Fernando have discussed.

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    Replies
    1. Arczed31 July 2016 at 23:31

      Hi Teddy! Earlier, Sir Fernando already discussed about it that although the Vin and Vout are on the same line which is positive, we must not combine or short it the Vin must be connected to the positive side of the Bigger Capacitor while the Vout must be connected to the positive side as well but on the Smaller Capacitor. When we combine the Vin and Vout on the same line without connecting it on the accurate line, the current in the circuit will flow differently so there will be an instance that the circuit will not function correctly because some components were disregarded. We will explain it furthermore on Wednesday. :)

      Delete
  6. Unknown30 July 2016 at 21:20

    Hi mam is the LM317 is easy to heat?

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    Replies
    1. Arczed31 July 2016 at 21:51

      Hello Chistian! It depends upon the time it took and the temperature that is passing through the circuit up to the LM317. If the temperature of the LM317 exceed to 60 degrees Celcius then heatsink is required so that it will avoid overheating. :)

      Delete
  7. Jalilah Batao31 July 2016 at 08:23

    Hi mam !
    Why does the LM317 requires a heat sink ?


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    Replies
    1. Arczed31 July 2016 at 21:46

      Hello Jalilah! An LM317 can safely be used to dissipate up to 0.25 Watts without any external heatsinking. When the LM317 reaches and exceeds to a higher amount of watts it will cause the LM317 to overheat. Typically you do not want a regulator chip to run at over 60 degrees Celcius. Therefore a heat sink should be chosen such that its thermal resistance will keep the temperature of the attached regulator below that maximum tolerable temperature. :)

      Delete
  8. Unknown2 August 2016 at 23:42

    Ms. Barro, can diodes be use as a voltage regulator?

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    Replies
    1. Arczed4 August 2016 at 19:23

      Hi Mr. Molina. Yes actually Zener Diode is an example or a type of diode that actually functions as a voltage regulator. :)

      Delete
  9. Rolando B. Cumilang Jr.4 August 2016 at 04:49

    Hi maam., incase of troubleshooting, How to test or repair a power supply.?

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    Replies
    1. Arczed4 August 2016 at 19:25

      Hi Rolando! I think your question is not related to my topic. This topic is about the LM317 IC only.

      Delete
    2. Arczed4 August 2016 at 19:29

      But if you will really need an answer on that. You may visit this website and read further. Thanks :) http://www.talkingelectronics.com/projects/ThePowerSupply/Page80PowerSupplyP2.html

      Delete
    3. Arczed4 August 2016 at 19:36

      This website may also help you. I hope you'll read it. http://www.bkprecision.com/support/downloads/power-supply-guide.html

      Delete
    4. Rolando B. Cumilang Jr.7 August 2016 at 00:02

      thanks po maam., pcnxa na po, naligaw ung tanong ko.,

      Delete
    5. Rolando B. Cumilang Jr.7 August 2016 at 00:37

      Hi maam., ito na po ung tanong ko., may possibility ba na ang Output voltage ng LM317 ay pweding ma.adjust down to 0 volts.?,

      Delete
    6. Arczed7 August 2016 at 21:27

      It's alright Rolando! I understand :)

      Delete
    7. Arczed7 August 2016 at 21:34

      Yes through connecting it to a potentiometer that you may use to vary the voltage from its maximum voltage down to 0 volts :)

      Delete
  10. Unknown4 August 2016 at 05:08

    how can we know if our power supply is in good condition '?

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    Replies
    1. Arczed4 August 2016 at 19:31

      Hi Vin! It seems that you are off-topic because your question is about power supply but my topic is about LM317 IC that acts as a voltage regulator.

      Delete
    2. Arczed4 August 2016 at 19:36

      But we can know if our Power Supply is in good condition when it is without doubt Working Properly and Accurately. :)

      Delete
  11. Unknown6 August 2016 at 05:38

    maam ehm the voltage from input is the same voltage when pass through in the ouput?


    -lacar

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    Replies
    1. Arczed6 August 2016 at 06:35

      Hi Lacar! Yes, the voltage that is passing through the input will be the same as the voltage coming out. The only difference is that, since you are going to use a Potentiometer switch. The voltage will vary depending on the switch.

      Delete
  12. Unknown6 August 2016 at 05:39

    maam ehm the voltage from input is the same voltage when pass through in the ouput?


    -lacar

    ReplyDelete
    Replies
    1. Arczed6 August 2016 at 06:35

      Hi Lacar! Yes, the voltage that is passing through the input will be the same as the voltage coming out. The only difference is that, since you are going to use a Potentiometer switch. The voltage will vary depending on the switch.

      Delete
    2. Arczed6 August 2016 at 06:40

      If you really want to know, maybe this website will help you. http://www.dummies.com/how-to/content/electronics-components-popular-integrated-circuits.html :)

      Delete
  13. Anonymous16 January 2018 at 10:26

    الـ LM317 يقوم بعملية تنظيم جهد موجب قابل للتعديل Variable Voltage. ذو ثلاث اطراف ( input, adj, output) وله القدرة على توليد اكثر من 1.5 امبير مع تنظيم جهد Output 1.25 فولت إلى 37 فولت كحد اقصى

    ReplyDelete

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