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decoupling capacitors to ground or supply voltage?

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vaah

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Hi

Very basic question,

What power line do you connect your decoupling capacitor(s) to, ground or supply voltage?

For example, say I have a reference voltage (Vref) and want to stabilize the voltage using a bypass (decoupling) capacitors. What should I consider when connecting the other end of the capacitor to the power line?
 

Hi,

Connect the capacitor to the node where Vref is referenced to.
In most cases this is GND .... but not always.

Klaus
 

You should consider, from the recipient's "point of view"
what is the prime reference ground. If the "vref" is
developed against ground plane then the recipient ought
to use the same ground plane and any filtering also
returned to it.

When you get to remote or even differently-established
ground domains, it gets real messy.

In IC internal designs I have often "decoupled" bandgap
voltage reference nodes to local signal ground, and made
"images" sent up to the high side and then decoupled
there for high-side-referred voltage reference.

What makes the current loop (of the decoupling cap)
the shortest and least area?

What are the noise aggressor sources and how do they
relate to the input and ground paths, to be snubbed?
 

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