LM7805 and L7805 - Page 1
Forum section: electronics / beginners

author: eeguy
author_rank: Regular Contributor
timestamp: January 24, 2024, 05:58:10 am
content: Hi, I am supposed to get a LM7805 but in a local store, it has L7805 only. Is it better to get LM7805 rather than L7805? I plan to attach a heatsink to whichever I end up buying.

author: selcuk
author_rank: Frequent Contributor
timestamp: January 24, 2024, 06:17:10 am
content: They are the same. Check whether the footprint and tolerance match with your requirement.

author: MrAl
author_rank: Super Contributor
timestamp: January 24, 2024, 07:02:45 am
content: Quote from: eeguy on January 24, 2024, 05:58:10 amCheck that they are in the same package type.They come in various package types, one is completely metal TO3 and the other is partly plastic. The metal one handles more power.There are also the low power versions that usually include an "L" alone and that's why I am mentioning this. The part number usually has the "L" in the middle though like this: "78L05" and that would be for lower output current like maybe 100ma or less. It's also in a small package like TO22 or something like that

author: Siwastaja
author_rank: Super Contributor
timestamp: January 24, 2024, 07:21:01 am
content: Rest of the letters are more important. LM7805 or L7805 are not full part numbers.LM- and L- are just from different manufacturers. They have tiny differences which might matter in some really specific design but usually not. If it matters, usually designer makes a clear note about it ("careful: no substitutions; National Semi's part used because of parameter XYZ...")Rest of the letters denote stuff like current capability, IC package (size, shape and pinout) which are hugely important; or temperature ranges, accuracy etc. which usually are important, too.Most importantly though, make sure you are not getting counterfeits. Ebay is nearly guaranteed failure, local stores are iffy but if this is all you have, go for it and hope for the best. 78xx series are one of the most counterfeit ICs because the IC is quite simple. Counterfeits sometimes work seemingly fine but may have lower current capability, or lack some protection features.

author: Ian.M
author_rank: Super Contributor
timestamp: January 24, 2024, 07:30:25 am
content: A couple of other middle letters:78S05 - capable of 2A if given good enough heatsinking. Needs a bit more headroom at rated current.78M05 - the 500mA variant.

author: MrAl
author_rank: Super Contributor
timestamp: January 24, 2024, 01:08:58 pm
content: Hello again,I almost forgot to mention, the 7805 regulator is not that good of a regulator as the tolerance is something like 5 percent. There are much better regulators out there now. The 7805 is an old regulator from the 1970's or even sooner.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: January 24, 2024, 01:12:58 pm
content: Quote from: MrAl on January 24, 2024, 01:08:58 pmWhich regulators would you recommend instead?

author: MrAl
author_rank: Super Contributor
timestamp: January 24, 2024, 01:55:26 pm
content: Quote from: YurkshireLad on January 24, 2024, 01:12:58 pmHow much current do you need to draw from it, and do you only need 5 volts output or would you like an adjustable version?Also, what is the input voltage?

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: January 24, 2024, 01:58:54 pm
content: Quote from: MrAl on January 24, 2024, 01:55:26 pmI don't have specifics. I thought it would be useful to identify the better alternatives, for beginners like me. You left us hanging...

author: Grandchuck
author_rank: Super Contributor
timestamp: January 24, 2024, 02:22:17 pm
content: TSR1-2450

author: eeguy
author_rank: Regular Contributor
timestamp: January 24, 2024, 04:37:53 pm
content: Quote from: Siwastaja on January 24, 2024, 07:21:01 amThe designer only stated getting a LM7805 or an equivalent buck converter, no more details on current capability, IC package, etc. He did mention that he got a buck converter from Murata to avoid heat. Here is a photo of the component he used.From the photo, can anybody tell exactly which product this is?This looks similar to:https://uk.rs-online.com/web/p/switching-regulators/7962132Both have I50115 on it but the bottom code is different. The one used by the designer has "08FC C" at the bottom but the one sold via rs-online has "95NC C" on it. What are these codes?

author: selcuk
author_rank: Frequent Contributor
timestamp: January 24, 2024, 06:59:12 pm
content: Yes. It is OKI-78SR-5/1.5-W36-C. Bottom line is manufacturing date code. Not a different part number.And this should be better than a 7805 in terms of efficiency.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 24, 2024, 10:12:13 pm
content: Also, not all LM7805 IC's are equal. Even if you stick with the most common TO220 package, different manufactures may use the same type number for (slightly) different IC's. I also guess that a "modern" LM7805 is a bit different from an LM7805 made in the '80-ies. These low transistor count and high current devices probably do not go though a die-shrink, but there may be other optimisations, or adaptations to other manufacturing processes.It's tempting to order an LM7805 just because it's a well known type number, but there are pin compatible improved versions with different type numbers too.

author: MrAl
author_rank: Super Contributor
timestamp: January 25, 2024, 02:31:00 pm
content: Quote from: YurkshireLad on January 24, 2024, 01:58:54 pmWell with something like this you have to be specific because each regulator is designed for a certain purpose. For example, and LDO regulator.The input and output voltage and output current is also necessary because there are so many types with fixed outputs and variable outputs.An example might be the MIC2940A-5 but you'd have to look that up to see if it fits your application.A more common example is the LM317 and as long as you do not let it get too hot you can get a more accurate output tolerance.There is also the type that has very low quiescent current draw, which is needed for battery operation.If you are just starting out in electronics though I would recommend starting with the LM317. You can set the output with just two resistors, and that means you can get a lot of different output voltages that way with just a change of one resistor (the bottom one).This is a common linear regulator among electronics hobbyists and it is also used in professional designs.