555 timer, pin 5, control voltage, capacitor 10 or 100 nF?

[AndersJ]

The CV capacitor is ”always” 10 nF?

I want to use 100 nF, to avoid a single 10 nF cap in the BOM.
MUST it be 10 nF?

[Mechatrommer]

no. it can be left open.

[Audioguru]

Pin 5 on a 555 is a simple resistor voltage divider for its voltage reference. 100nF is fine as a filter if you want it filtered. Use thousands of microfarads if you want but it will take all day to turn on.

[danadak]

Look in data sheet and you will see control voltage pin, if unused, bypassed
by .01 uF. That's to avoid having output modulated by stray coupling to that
pin. Note it has to be AC bypassed, you can't connect pin to either rail because
its part of an internal biasing network.

Note the pin is relatively low Z, that's why I think community has been able to
get away without bypassing, eg. coupling has to be pretty significant to affect
the pin. But best practice bypass it.

Regards, Dana.