Showing results for 
Search instead for 
Did you mean: 

What is the best location to place an ECMF on PCB?

ST Employee

What is the best location to place an ECMF on PCB?

What is the best location to place an ECMF on PCB?

Our best recommendation is to put our ECMF close to the connector, however for some application we are open to discuss with customers about possible configuration with ECMF close the transceiver
CF AN4511 on Common Mode Filters
It’s important to connect +8kV ESD protection of the ECMF on connector side instead of IC side.

Do we have some constraint about PCB layout?

  • Regarding PCB layout, the differential lines need to be matched to 90 Ω or 100 Ω differential characteristic impedance.
  • Keep as much as possible the same length between both differential lines to minimize skew.
  • ECMF connection to ground need to be as short as possible, with multiple vias to minimize parasitic inductance
  • Finally, you need to place the ECMF as close as possible to ESD source: this minimizes the line inductance and the EMI on the PCB, couplings with other tracks
  • You can look on the AN5686: PCB layout tips to maximize ESD protection efficiency for more information.

Do you have application notes to help to design?

The application notes related to STMicroelectronics ECMF are located in Common mode filters with integrated ESD protection  
Additional product information available here.
Version history
Last update:
‎2022-09-02 03:20 AM
Updated by: