Electronics > Beginners
Recreating mod chip designed for the Playstation 1.
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Katcher:

--- Quote from: KL27x on November 05, 2018, 11:25:36 pm ---"Routing" has two meanings here. Signal routing in software is the one thing. But in the other post I was referring to the board outline being routed by a CNC milling bit, vs V-score, which is making a V shaped groove partway through the PCB material. The cost for tab routing isn't really anything to write home about, but the kerf can add up when the board is so tiny.

Not that it matters if you are just making 10 board for yourself. Go nuts.

The way you did the capacitor is totally fine, but you could also make a more direct connection for the caps, if you wanted the absolute minimum ESR for your decoupling cap. It really doesn't matter; just a note because you asked.

--- End quote ---

Oh yeah I'm only gonna be making maybe 10-15 of these things since I'll most likely bugger up a few during assembly. Taking what you've said I've come close to what I'm considering the final design. I could probably do with moving the trace from PAD_5 along to the left just a bit but I feel everything else is fine. I could use a second opinion though.




--- Quote from: james_s on November 05, 2018, 11:30:13 pm ---A decouple capacitor should always be wired directly to the power and ground pins of an IC, as short and direct as possible. In this application it is probably not critical but in things that really need good decoupling those long spindley traces between the IC pins and capacitor would wreak havoc.

--- End quote ---

Mate. There is no way in hell I'm getting the decoupling capacitor that close to those pins. I believe I've already said that. I have however connected it directly to the proper pins this time with the pads connected to those traces. I have no fucking idea if it will work but if it does...yay.
Mr. Scram:
It seems you could do quite a bit better than that. As people have stated correctly already, rotating the MCU on the board would probably save you loads of headaches. Decoupling pads need to be connected as directly as possible without unnecessary loops, so even if you're insisting on the complicated design it really pays to connect the VSS_B decoupling pad and the VSS_B IC pad together with a direct path. Just straight from one to the other without looping around.
Katcher:

--- Quote from: Mr. Scram on November 05, 2018, 11:47:33 pm ---It seems you could do quite a bit better than that. As people have stated correctly already, rotating the MCU on the board would probably save you loads of headaches. Decoupling pads need to be connected as directly as possible without unnecessary loops, so even if you're insisting on the complicated design it really pays to connect the VSS_B decoupling pad and the VSS_B IC pad together with a direct path. Just straight from one to the other without looping around.

--- End quote ---

I appreciate you saying I can do better. I know I can. And I do sort of understand why the decoupler needs to be connected as directly as possible just not exactly WHY it needs to be. I haven't the slightest fucking idea what I'm doing and it's great. However. This is a tiny ass 11x11mm board. I've got to factor in the size of the components and the pads and the space in which the fully assembled modchip has to occupy. The thing is only a single layer as well. If this was a much physically larger project then I'd be doing what I can to get the decoupler as close and as directly linked to the VSS and VDD pins as possible. I know that from looking at what I have right now I can make a more direct connection between VSS_8(Not B btw. It's an 8. Numbering the pins/pads to keep track of what goes where.) and the decoupler. But it isn't feasible to make a more direct connection between Pad 1 and VDD_1 with this design. I'd go for a more rectangular design over a square one if I could but due to needing it to have as small a profile as possible, I can't.
Mr. Scram:

--- Quote from: Katcher on November 06, 2018, 12:06:47 am ---I appreciate you saying I can do better. I know I can. And I do sort of understand why the decoupler needs to be connected as directly as possible just not exactly WHY it needs to be. I haven't the slightest fucking idea what I'm doing and it's great. However. This is a tiny ass 11x11mm board. I've got to factor in the size of the components and the pads and the space in which the fully assembled modchip has to occupy. The thing is only a single layer as well. If this was a much physically larger project then I'd be doing what I can to get the decoupler as close and as directly linked to the VSS and VDD pins as possible. I know that from looking at what I have right now I can make a more direct connection between VSS_8(Not B btw. It's an 8. Numbering the pins/pads to keep track of what goes where.) and the decoupler. But it isn't feasible to make a more direct connection between Pad 1 and VDD_1 with this design. I'd go for a more rectangular design over a square one if I could but due to needing it to have as small a profile as possible, I can't.

--- End quote ---
I'm not sure why you'd want to give yourself trouble by using the sideways design. This means traces have to go all over the board, probably requiring more space than would otherwise be the case. Can you explain?
Katcher:
You can see the image right? The traces are running under the IC to connect to each pin once the IC is soldered in place. If I were to rotate the IC 90 degrees to the left I'd then have to elongate the PCB width-wise, I DON'T want to do that because space(Also see my hilariously poor Space Invader shaped PCB a few posts ago. Looks great, probably isn't ideal). Did I also mention I'm trying to make it as COMPACT as possible too? An 11x11mm PCB is as small as I can make it without running into issue. And given how damn tiny that is I don't really think the distance between decoupler and pins is a really big deal. I'm not having trouble with this design at all frankly and it doesn't seem the maker of the original design or those who have bought a fully assembled modchip and actually used it had trouble either. Sorry if I sound a bit arsey here. I get you're giving me advice I can use with future projects but there's just no way I can get the decoupler any closer than it is using this design.
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