I am looking at a 3-pad SMD EMI filter chip (see photo) which is marked on the top with "222J". I am familiar with reading the markings on top of resistors and capacitors, but am not sure how to interpret the markings on a EMI/RFI filter.
This is an LC feedthru filter which means it is bidirectional.
They cannot control the ferrite inductance L and loss values with J accuracy but they can control the buried cap value.
So one vendor may have a slightly different Series Resonant Frequency than another.
But this TDK part guarantees at least 25 dB attenuation into 50 Ohms from 45 to 105 MHz. Actual could be as much as 30 MHz to 300 MHz for the TDK part.