Mfcttrf

I have a datasheet that calls for "a 15 pF capacitor with Self-Resonant Frequency in the 1800/1900 MHz range". It then recommends a capacitor (Murata GRM1555C1H150J) that (so far as I can tell) from the datasheet doesn't specify it's SRF.

I'd like to use a different, slightly larger SMT capacitor, but I understand this may lower (or just change) the SRF.

Mouser's part search engine doesn't include an SRF parameter. Is there some way to obtain capacitors with a specific SRF? Can the SRF be reliably derived in some way? Or does this property have to be measured?

You need to use Murata Simsurfer (or the equivalent from another vendor) that provides the REAL datasheet (so-called tech-PDF in Murata's case) for the individual capacitor's detailed curves. That's where you will find the datasheet for the GRM1555C1H150J and its SRF:

What you are probably looking at right now is not the datasheet but the catalog where they cannot afford to actually list the datasheets for thousands of different capacitor with different combinations of capacitance, package, voltage, and dielectric.

Taken from Murata Tech-PDF for GRM1555C1H150J.

I think they are fairly representative from one manufacturer to the next though for a given dielectric and package size so if you can't find it for one dielectric in a package size, you might not find it for any manufacturer unless you change dieelectrics.

https://ds.murata.co.jp/simsurfing/mlcc.html?lcid=en-us

Most capacitor manufactures will list these parameters on their website which they have measured. Most of them will also provide spice models (use lt spice, it's free), s-parameter models and other tools to help you model the effects of parasitics at high frequencies.

The Simsurfing web tool from Murata that @DKNguyen mentioned is my weapon of choice for problems like this. Other manufacturers may offer somewhat similar tools, but none as convenient as Murata's.

Addressing issues not yet mentioned in the other replies:

• the particular part that was recommended (GRM1555C1H150J - 0402 size) has SRF ~2.05GHz, a little higher than you're looking for. Besides, this part is not recommended for new designs. You're better off using the bigger 0603 part GRM1885C2E150JW07, with SRF ~1.75GHz.


• as a first order approximation, you may assume that the parasitic inductance is more or less constant for a given package size and dielectric. This way, if you know the SRF of a particular capacitance value, you can estimate the SRF for other capacitance values within the same series. I find it easier to use the tool interactively, though.


• the bigger the package, the bigger the parasitic inductance, and the lower the SRF; for really low inductance, high SRF, there are special packages with the pad side along the longest dimension of the package.


• unfortunately, the SRF always changes a little from manufacturer to manufacturer even for the same ceramic and package size. If SRF is really critical for your circuit, I recommend sticking to a single manufacturer.