I am just starter working with PRoC, so please excuse me for maybe trivial question but could you help me to understand why specification (CYBLE-022001-00 ) said that one of two ferrite beads need to be used for power supply of the module ( see picture attached ), and why only this specific ferrite BLM21PG331SN1D from Murata need to be used?
so in general my questions are:
a) What use cases of module drive to use single or double ferrites?
b) Why this specific Ferrite need to be used? Is it related to FCC to provide necessary filtering for the radio? If the filters could be used different and if yes which parameters are critical?
Even if the module is very small 1cm x 1cm in application I have to guarantee the additional space for those ferrites so please help me to understand the background of this proposal.
Thank you very much
The ferrite bead is used to filter out noise from the power suppy to reach the module, and to filter RF noise that might come from the EZ-BLE to reach the outside world.
This is good practice to ensure maximum performance of the module, and to ensure EMC compliance. I don't think there is a hard requirement to use only this one ferrite bead - any other one with similar specs should work. Its just that Cypress tested with this bead and knows that it works as it should - if you want to use another one you need to do your own testing.
Thanks a lot for explanation. However I am still curious what lead Cypress to suggest 2 ferrites in some applications and sometimes just 1 ferrite, and why this exact type. You mention about performance and EMC, which is great, but I would like to understand how much I loose without use the ferrites? There should be some test results available?
Knowing this limitations I could design power supply which might remove needs of those ferrites and/or I can have a reference point to evaluate a potential other ferrites for my application as you suggest.
Thanks a lot
Every single country has its own specs for EMC and rf noise you may produce, so what you need is to know your market and the specs. When in a very noisy environment (Fabric hall) you will have to do more to protect your circuits (not only those bearing a PSoC). When in a more delicate environment(Hospital) you will have to do more not to produce unwanted noise and to protect from injecting it into the power-line.. Board layout is a relevant factor for both cases. This also has nothing to do with PSoCs, it is a general question. So when you will bring your electronic product to market you may need to measure. This is nothing a reference datasheet will tell you.
Thanks a lot Bob,
So if I follow your explanation. The ferrites suggested by Cypress 2 or 1 ferrite and specific Murata one is just a suggestion/recommendation nothing else. If I will pass the necessary tests without ferrites I don't need to use them in the final application. Correct?
Thanks a lot
I don't need to use them in the final application. Correct?
As I said before: Without your design may disturb other devices or might get disturbed by others.