I have 2 li-ion 3.7v batterys running a 5v regulator and i want to put a on/off switch . It would be on the ground line and disconnecting ground basically to turn it off. My question is does it matter what the current rating of the on/off switch is ? Reason im asking is because id like to use a really micro sized toggle/slide switch .

 

You need a switch capable of handling the load current that 5V regulator delivers.

THAT is what the switch will interrupt.

If you would rather use a tiny switch, look into low drop out regulators: many come with an enable input that makes the regulator act as a switch. Typically these regulators draw very little current when disabled. That may be OK with your batteries.

 

Its actually a synconous buck regulator and yes it has a enable pin running a momentary switch .The momentary switch turns on the regulator when its pressed. The on/off switch is just so the regulator wont turn on in someones pocket. I know if i were to put the on/off switch on the power side it would need to be rated for the current draw but i thought if the on/off switch were on the ground side i wouldnt need to worry about the current draw.

So i cant use a small on/off switch? Iv never has a issue using the on/off switch on the negative side in one of those radioshack battery boxes but the switch i want to use is even smaller then that. Basically it would just cut the batterys from making a connection to the regulators ground wire

 

put the small switch in series with the momentory switch to switch the regulator off. Power ratings of a switch need to be the same whether they are put in +ve or 0ve. I very much doubt you have a ground(wrong term for 0ve ,ground is entirely different ).

 

...I know if i were to put the on/off switch on the power side it would need to be rated for the current draw but i thought if the on/off switch were on the ground side i wouldnt need to worry about the current draw...

Huh? Current comes in one side and leaves the other.

Ground has the same current as "the power side." Always.

 

Yes MANY people don't understand that the current is the same ALL the way around a circuit.. Not just up to the load.

 

Honestly thats what i thought too although i wasnt sure .Thats because i see people using the same circuit with small switch on the ground side to disconnect the circuit and thought,well if it works for these people maybe its ok.

I guess not.How quickly do you think they will burn out? Most people seem to be using the same .1 or .5A slide toggle switches.

The switch is really being used as a backup .The momentary switch keeps the circuit off and the toggle switch just makes sure the momentary switch cant activate the circuit.

 

The switch choice depends of at least two parameters that are important here: the surge current and the running current. You must meet both requirements. I would rate the switch for double the measured values to have a good margin.