Hi,
looks like we need to replace 0805 10µF ceramic caps with tantalum caps. (Reasons are outlined below). I'm am aware tantalum have the reputations of failing spectacularly*, but I wonder if this is still the case today? These are the parts we tested our circuit with and intend to use:
https://www.rohm.com/products/tantalum-capacitors/conductive-polymer-capacitors/tcto/tctop/tctop1a106m8r-productthanks
*and also of having negative impact on the environment
Reasons:
We have a voltage reference, but need half that voltage for bias purposes. This is achieved with a simple resistor divider, followed by a 10µF ceramic (X7R) cap. What could go wrong?
The boards are already manufactured and ready to be assembled. And of course now we realized there is a problem.
It is not the voltage dependency of the caps that causes problems, but their temperature stability.
The board warms up a bit when powered, about 50°C, if I now blow some air on it to cool it down, the voltage at the divider changes for a few seconds and then goes back to its original value. This is of course because the capacitor changes its capacitance which in turn changes the voltage at the divider for a short time.
Electrolytic caps do not show this problem. But these are not available in 0805 (as far as I know).
Not wanting to re-spin the board I tried tantalums and they also do not show the temperature dependency (at least not measurably in this setup)