MLCC caps in series

[SnakeBite]

Hi,

i saw in Dave's video about capacitor that if you put them in series you need to put balance resistors in parallel to them to avoid different voltage drop on the capacitors due to leakage. in the video he talks about electrolitic capacitor but do i need to do that with MLCC (multi layer ceramic capacitors) as well? bear in mind that the capacitors in my design is not used in high current or high voltage they just audio signal capacitors (filters). i'm putting them in series to get smaller capacitance.

thanks
Ido

[Paul Price]

no, not necessary to use resistors at all because there are no high voltages to distribute..

[ok_cool]

I continue on this.

So it is perfectly OK to use 16V ceramic caps in series to get higher than 16V? Looking to get 30V with 22µF ceramics.

[tautech]

I continue on this.

So it is perfectly OK to use 16V ceramic caps in series to get higher than 16V? Looking to get 30V with 22µF ceramics.

Yes, but for 2 caps the total capacitance is havled:
http://farside.ph.utexas.edu/teaching/302l/lectures/node46.html

[T3sl4co1l]

Arguably, it might be more important, because although the leakage is lower (uA?), there isn't a self-balancing effect to it.  And if one capacitor eventually ends up overcharged, its capacitance (and therefore the total capacitance) will drop precipitously , as the dielectric saturates.  (There's absolutely no danger of breakdown -- a 16V cap might finally arc over beyond 100V.)  So you'd still want resistors, but the values can be larger because the expected leakage is smaller.

I would much better recommend using good old electrolytic or tantalum for your purpose, or if low ESR is needed, aluminum polymer.

Tim

[ConKbot]

Be mindful that with dc bias, or if you're feeding that much signal in that you're needing 2 caps in series that high capacitance ceramic caps (x5r/x7r and related, and even more so y5v and z5u), the capacitance changes with voltage applied. Plus they can be microphonic.  For filters and stuff in the signal path, stick with c0g/np0 ceramics or film capacitors.