Add the TI TS3A27518E 6-channel 1:2 analog mux

[jonas-schievink]

This adds the WQFN and TSSOP packages. There's also a BGA variant using "24-pin BGA Microstar Junior", which not in the footprint library. I might add that in a later PR, but for now these 2 variants should be fine.

Footprint PR: KiCad/kicad-footprints#1785

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All contributions to the kicad library must follow the KiCad library convention

Thanks for creating a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items:

• Provide a URL to a datasheet for the symbol(s) you are contributing
  • http://www.ti.com/lit/ds/symlink/ts3a27518e.pdf
• An example screenshot image is very helpful
• Ensure that the associated footprints match the official footprint library
  • A new fitting footprint must be submitted if the library does not yet contain one.
• If there are matching footprint PRs, provide link(s) as appropriate
• Check the output of the Travis automated check scripts - fix any errors as required
• Give a reason behind any intentional library convention rule violation.

[chschlue]

• Add packages to the descriptions
• WQFN EP is too large
• BGA is EOL, can probably be left out
• : is disallowed

[jonas-schievink]

WQFN EP is too large

True, 2.6mm instead of 2.45mm. Do you usually create an entirely new footprint in this case?

: is disallowed

Do you mean in the symbol description? (the guidelines don't mention this, they only say what's disallowed in symbol names)

[chschlue]

True, 2.6mm instead of 2.45mm. Do you usually create an entirely new footprint in this case?

Easier than it sounds, QFN footprints are scripted.
You basically add it to https://github.com/pointhi/kicad-footprint-generator/blob/master/scripts/Packages/Package_NoLead__DFN_QFN_LGA_SON/size_definitions/qfn/wqfn.yaml , generate it, create an FP PR and cross-reference them (generator, FP and symbol PRs)

Do you mean in the symbol description? (the guidelines don't mention this, they only say what's disallowed in symbol names)

That should probably be clarified.

[chschlue]

• NC pin may be connected to GND
• EP should be connected to GND

[jonas-schievink]

I think I didn't do the N.C. pin right. What electrical type should it get? Is "Not Connected" right?

Oh, also:

Pin GND (25) : POWER INPUT should be visible (power-in/power-out pins may never be invisible, unless in a power-net tag/symbol)

Should the EP not be set as "Power Input"? Ah, it should be set to "Passive" according to http://kicad-pcb.org/libraries/klc/S4.3/

[chschlue]

You could set it to invisible, type NC and place its end on the symbol outline.
That way it's out of the way but still able to be connected if one really wants to.

[poeschlr]

NC pins must be set to invisible and placed inside the symbol outline (or on the outline itself depending on if the outline is on the grid for pins)

See: KiCad/kicad-website#377 for a clarified version of the NC pin rule set.

[chschlue]

Apart from the fact that invisible and placed inside the symbol outline is the current state of this PR, you can't expect anyone to follow future KLC versions.

[poeschlr]

I only clarified that "should" simply is not strong enough. The KLC rules were sadly written in polite voice. In reality however this is a "must" rule. (which is what i intended to both clarify in the rule update and in my comment.)

Edit: regarding the "inside the symbol part": pins must still be on the outline if said outline is on the grid. (My wording in my comment here was indeed ambiguous, the rule update however makes this clear.)

[jonas-schievink]

See: KiCad/kicad-website#377 for a clarified version of the NC pin rule set.

Thanks, that's helpful.

I've fixed the remaining warnings in the CI script and also updated the screenshot to reduce confusion.

[chschlue]

Keywords must be separated by spaces. Everything else looks nice.
Edit: TI as a keyword is unnecessary.