Need help with schematic dimensions please

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#1
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I am trying to create a PCB in Eagle Cad for the following IC.
http://download.cypress.com.edgesuite.net/design_resources/datasheets/contents/cyons1001_8.pdf?key=1232752110571
The attached "Other_Drawing.PDF" is the drawing only from the MFR which is much clearer than the drawing in the datasheet. Page 19, Figures 12 and 13 show the keep-outs. The way the drawings base the dimensions for the keep-outs on a hole that is in the chip makes it very difficult to read. I have never made a PCB before and I am new to Eagle Cad but learning. Could someone please look at my drawing and confim my dimensions please.
Thanks :)

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Can't someone please help me with this, I don't want to bother the mfr. and I don't want to spend time in Eagle using the wrong dimensions and then spending money getting a board made thats wrong.

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Why don't you place the device on a board and print it on a sheet of paper? Then place the physical device on it and see if the dimensions are correct. That's how I do it.

Only make sure you don't scale the drawing when you print.

pycrc -- a free CRC calculator and C source code generator

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That will work for the chip but there are also two millings and four keep-outs.

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I guess that the dimmentiones of the schematics are irelevant.

HM

HM

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Why do you say that? I don't understand what you mean.

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schematics are for the electrical side of things - these are irrelevant for the question you ask.

The first drawing seems straightforward enough for me - the cutouts are referenced to a pad - what is the issue here? That pad has a location - reference from that.

The cutouts are usually on their own layer - mech layer1 in Protel. Can you not print out a composite to check the dimensions? As for the keep-outs - you can decide whether you want to include them or not. If you don't include them, make sure you don't route tracks in that area!

If you're new to doing pcbs - expect to make mistakes. Its not an easy task.

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Ok, I see what you're saying. I worded that poorly. I didn't mean schematics, I meant drawings. As I said it's the fact their basing all the measurements from one of the holes in the chip instead the center of the chip. I'am having a difficult time telling what points to what, especially with the blurry drawing. In Eagle the cutouts are also on a different layer "milling" but I still need to know their location either from the hole they use as (0,0) or the center of the chip for them to be positioned accuratelly. I have the IC but not the lens clip, it's still on order. They have a very long lead time. I don't want to just eye the fit. As I said I am a beginner with Eagle and PCB layout so the drawing dimensions are not straight forwared to me. Have you looked at the data sheet and my drawing? Can you just tell me if it is correct please?

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What I do with a complicated footprint like that is insert dimensions for the various pads and cutouts into the footprint, so that I can check them against the data sheet.

Leon

Leon Heller G1HSM

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I recreated the drawing as you sugessted. I'am ok on the pad dimensions and their locations. I'am unsure of the locations for the tab in the center of the chip and the cutouts. I don't understand what is pointing to what.

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Please help :cry:

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Two weeks and no solution! Time to take a leap of faith. Trying to get 100% on a circuit board with little experience is asking a bit much. Aim to get it as good as you can, spin the board and learn from your mistakes. Otherwise it will be a month, year etc and you'll still be pondering over the same problem. Do your best and see what happens.