pentiumspeed wrote on 2022-06-19, 23:32:
Always derate the amps or watts by certain % for headroom if datasheet did not specify derating. Say you have this module rated up to 12 amps, I call this up to 10 amps times 2.0V, 20W total, For 3.3V, this is 33W. Good to include a jumper if you can to get it to 3.5V or so for some CPUs. Efficiency goes up with higher input voltage which is in your case it takes 12V which is included in the VRM module pinout, at 5V input, it might get bit more warmer.
This is why I searched and purchased few modules that is rated for 16A max so I allow for my similar projects to have 14A and another module rated for 30A (has two inductors).
Cheers,
Fair point and I have been keeping that in mind some at least some bit.
My knowledge of dc/dc modules is very limited and I'm very sceptical of many dc/dc modules, the only brand I know in the scene that's well regarded is muRata. They have a 12amp module that fits where I need it and I've seen in another thread that the 20amp module was being used in a similar scenario.
This is aimed to my board that has 2 VRM units, one with a large heatsink that steps 5v down to 3.5ish or 3.3ish, then a much smaller second one for dual voltage cpus that steps the voltage from the first vrm down to core voltage.
I can set the second vrm to be bypassed so the first vrm handles the 3.5ish, though this can do 3.5 with switches 1 & 3.
There is also a jumper on the back of the smaller vrm that lets me switch between 5v and output of vrm 1 for the input of vrm2. As a consequence I could pump 12 v in through there and I'm toying with adding like a solder pad or something to this device as a shortcut to add 12v. It's a small board, finding space is getting difficult. I wrote 5v on the schematic because the original vrm circuitry that used linear regulators ran off of the 5v rail.
If it isn't obvious, this module is aimed to replace vrm2 (the smaller vrm) that generates the core voltage.
Now onto numbers and this is where things get a little self-centered;
The most power hungry CPU that I ordered and will use if everything works, is an AMD k6 500mhz. I might try others just for fun but I'm assuming that this k6 will live in the board.
Going off of the data found on CPU world, the CPU is a 2.2v CPU that consumes a max of 20.75 watts, that works out to just under 9.5 amps which is just a hair under the 10amp ceiling that you seem to be suggesting. This would be pushing the CPU as hard as it can go which is something I personally wouldn't be doing much of. For retro computing I just want something with a bit more kick than my 486 100mhz CPU .
For 2.0v cpus that want over 10amps, you'd definitely want to look at the 20 amp unit at least, though I'd worry about the traces on the actual motherboard being an issue if the stock vrm couldn't deliver that kind of power.
I think that addresses everything, thanks for your comment!
-Lime
PS: I'm not sure I can fit the 20amp version of this module but I might give it a try.
Be Happy, it's only going to get worse.
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