Is there a general rule of thumb for choosing the voltage rating for multilayer capacitors? Twice the expected voltage maybe?
This has to do specifically with an LCD where the generated voltages are as high as 12.5V, at least in the steady-state.
Twice the expected voltage is a good choice.
You mention voltages as high as 12.5v. Have you used a voltmeter to verify that is the highest it goes. Many systems/batteries/solar panels that are rated at 12v, will actually go a bit higher, like 14.8v, or 18v.
I like to use caps with voltage rating about twice what the systems are rated at.
The genral rule is to run the capacitors at 80% at most of the rated value.
Yes, the capacitor with the highest voltage is 12.6V as measured on my DMM. But I don't know if it never goes higher. Maybe when it's first starting? I don't know that.
I've never ordered SMD caps before and there are about twenty zillion to choose from. This will probably end up being an iterative process but I'd just as soon not fry any.
Thanks.
I haven't done SMD.
with about twenty zillion to choose from, why not use one of higher voltage. Is it a space issue on the board?
What do you think would be your best bet?
Capacitors are often given a working voltage - you can run them at this voltage indefinitely
in theory, but everyone likes a bit more safety margin - usually the next voltage up is high enough anyway,
16V is the next one up for electrolytics, and MLCC's are normally 25V/50V/100V
Ceramics (except the low value ones which are an entirely different dielectric) are non-linear, so
if linearity at all matters, rate the voltage very conservatively and stay well below the max voltage.
If you have significant energy storage requirements economics dictates you choose the smallest
voltage rating that is adequate as cost/size scales with voltage squared.
Thanks. It's still a bewildering number of choices to make. I think I'll order 50V rated capacitors. They're the same dimensions and roughly the same cost as the 25V versions. I can't see what the downside is.
If the price is not a problem, and they fit on your board, then I would agree .