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Im designing a DC-DC voltage step down regulator based off of a switching regulator IC from texas instruments. I have designed the schematic and board accordingly and it should be able to supply 5A at 5v (According to the IC)

enter image description here

Above is the board ive designed on EAGLE. I'm very new to PCB design and my worry is the board may heat up. The IC says it can handle 5A but it is so small as well as each trace being thin. I know there are trace width calculators but I dont know what 'Input Thickness' is. Can someone explain how I would find out how each thick each trace that will be delivering high current should be and also if the IC will heat up and what I could implement to prevent that? Thanks.

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  • \$\begingroup\$ digikey.co.nz/en/resources/conversion-calculators/… \$\endgroup\$ – Bruce Abbott Aug 24 at 23:25
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    \$\begingroup\$ Did you read the datasheet PCB layout guide? To me it seems almost all points need improvement. Thickness is the copper thickness of the PCB, there are usually few different options available when ordering, so check what options you have or assume you get less thick copper. \$\endgroup\$ – Justme Aug 24 at 23:27
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    \$\begingroup\$ Yep, that layout is awful. Look at the layout guidelines or use the TI Webench tool, which will give you a PCB layout as well. It takes practice and experience to do good analog and power layouts, so don't be discouraged. \$\endgroup\$ – John D Aug 25 at 1:10
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Trace thickness is the thickness of the copper layer. In the US you order that by "ounces", which really means ounces per square foot. If your calculator wants the thickness in mm or inches, look up the conversion.

Just to complicate things, you can order different copper thicknesses. The typical thickness is 1 ounce, and it's common to get thicker copper. If you're buying from a PCB aggregator, then you're going to get what they supply (probably 1 ounce).

You're concerned with the trace width, which hopefully you now have enough information to figure out.

I strongly suggest that you look at the layout guidelines on the datasheet. Switching supplies like this have high-current, high-frequency signals on them, and layout is not trivial. You need to think about where the current is going to go during each phase of the switcher's PWM cycle, and make sure it can get there. Starting with TI's layout example is a really good idea.

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    \$\begingroup\$ For reference, 1 oz/ft² is (almost) 35 microns, and is usually quoted as 35µm. \$\endgroup\$ – marcelm Aug 25 at 0:17
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Here is a useful number for you: standard PCB foil (default is 1 ounce of copper per square foot of area) has thermal resistance of 70 degree Centigrade per watt, per square of foil.

how much heat so you need to remove from the IC?

How much heat do you need to remove from schottky diodes?

From the MOSFET switch?

Per the datasheet, the main heat-exit paths are Vin and GND.

Reading the TI datasheet, you have violated the layout, where the suggested layout has GROUND extending under the IC, and wide.

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On top of what @TimWescott already answered, you can also solder along the traces to allow for more current to pass through that trace. This is common practice especially with UPS board that usually have high current traces running through it. Here's a good example of a tinned PCB that can handle more current than untinned traces.

https://www.eevblog.com/forum/blog/eevblog-317-pcb-tinning-myth-busting/?PHPSESSID=ar8b6g14n9noc61mss6d3nrm1v

Img src: https://www.eevblog.com/forum/blog/eevblog-317-pcb-tinning-myth-busting/?PHPSESSID=ar8b6g14n9noc61mss6d3nrm1v

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