MuRata passive component SPICE models

[Cerebus]

I thought that I'd just point up something I found the other day. MuRata have really comprehensive libraries of SPICE models available for their passive components, tailored to various SPICE simulators including LTSpice. Just look under the "Design Tools" tab on their website.

These include things such as modelling parasitics and, for the capacitors, voltage dependence of the dielectric for ceramic capacitors. The latter has a significant effect on the non-ideal behaviour of MLCCs versus their DC bias voltage and can make quite a difference in some circuits. Dave's done a video on this.

Here's an example of the effect feeding a 5V 500Hz square wave through 1K to a 100nF capacitor with different DC biases using both the MuRata model of a 100 nF 50V MLCC and the default LTSpice capacitor model.


Quite a significant effect. Not important all the time but it'll bite you on the bum on occasions. I wouldn't suggest using the detailed models of passives for every simulation - they slow things down significantly - but where you're relying on details such as filter and timing circuits it's well worth the effort.

[mikerj]

I recently discovered this very useful resource when I needed to model a specific Murata ferrite bead; trying to create a model based on the impedance plots on the datasheet was becoming very tedious.

The voltage dependence of ceramic caps is probably larger than most people realise!

http://www.murata.com/en-eu/tool