12V DC to DC buck converter LM2596 ADJ - Page 1
Forum section: electronics / beginners

author: misiek303
author_rank: Contributor
timestamp: April 28, 2023, 01:55:54 am
content: HiI put together a circuit with of LM2596 ADJ version. Can you guys have a look if I made any errors? You will probably notice that I added a 680uF cap instead of 220uF. I am not sure if that is right. It must hold high spikes, it will be used on the motorcycle.I followed the examples from the datasheet but the LM pin arrangement is different. I wonder if I made mistakes or if there is room for improvement.Thanks a lot?

author: Jwillis
author_rank: Super Contributor
timestamp: April 28, 2023, 02:25:14 am
content: There are only 5 active pins on a lm2596. To simplify you can omit pin 6. Not to say that you cant use the tab as a ground. But the circuit looks correct. The inductor is pretty high at 330uH . For 12V 33uH would be enough.Check the datasheet for inductor , diode and capacitor values for voltages and current requirements.https://www.ti.com/lit/ds/symlink/lm2596.pdf

author: Kane
author_rank: Contributor
timestamp: April 28, 2023, 03:04:50 am
content: Following section 9.2.2.2.2 for the inductor selection process gives you an E * T value of around 18.8 which puts you around where the red line is i've put on the inductor selection guide.So depending on your maximum load current pick 68, 47 or 33 uH.You can also buy LM2596 Modules off eBay for like £2 free shipping if thats an option for you.

author: misiek303
author_rank: Contributor
timestamp: April 28, 2023, 03:35:07 am
content: is 3A for the output or input ? - the motorcycle battery is 6A.

author: misiek303
author_rank: Contributor
timestamp: April 28, 2023, 03:39:17 am
content: Quote from: Jwillis on April 28, 2023, 02:25:14 amSorry, what do you mean by "tab" as a ground?

author: Eraldo
author_rank: Regular Contributor
timestamp: April 28, 2023, 07:33:40 am
content: Quote from: misiek303 on April 28, 2023, 03:35:07 amThe max output current is 3A, given you give it enough cooling. That's the limit and if you were to need more current in the output then just go for one of those ebay/amazon/aliexpress 300w buck converterts which can go up to 8A (they already have a small heatsink but make sure to test it out before use).There is also another 300w buck converter but with a higher current rating (smth like 20A)But if all you need is like 2 A, maybe 2.5A if you push it, then this chip is good enough.And if you wanted to build your own buck converter with high current capabilities, then just find the datasheet of the chips they use in their 300w models and continue from there. (The inductor of course will need to be bigger and be capable of handling that amount of current)

author: Jwillis
author_rank: Super Contributor
timestamp: April 28, 2023, 10:17:12 am
content: Quote from: misiek303 on April 28, 2023, 03:39:17 amhttps://www.ti.com/lit/ds/symlink/lm2596.pdf?ts=1682650896822page 4 tab is ground

author: misiek303
author_rank: Contributor
timestamp: April 28, 2023, 12:54:12 pm
content: Quote from: Jwillis on April 28, 2023, 10:17:12 amI see.So why do they labeled it as GND if I can't use it as a ground? - just curious.

author: Jwillis
author_rank: Super Contributor
timestamp: April 28, 2023, 06:45:34 pm
content: Quote from: misiek303 on April 28, 2023, 12:54:12 pmWhat's the point. Pin3 and the tab are connected internally. It's going to be connected to the ground plan anyway by the heat sinking . So to avoid confusion in your diagram the tab isn't usually used as a pin designation.