The figures in the datasheets are not always a complete schematic.
I'm assuming when you say "switch" you are referring to a mechanical switch (i.e. a toggle or some sort).
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if the addition of a switch suddenly starts creating noise then the switch or wiring is bad.
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you should have a capacitor from Pin 6 to Pin 4. I would suggest at least 1000µf + a 0.1µf