ZB1200-DE schematic

ZB1200-DE Coilcraft transformer has 3 windings, between pins 3 and 6, 1 and 4, and 1 and 6.
From the schematic provided in datasheets it is unclear what is the coupling between them.
Could you please help?
Cheers Jacek

Welcome to the Digikey tech forum. I may be wrong on this but looking at the datasheet it appears part ZB1200-DEC is a balun type transformer for balancing signals where part ZB1201-CEC is the coupling transformer which the datasheet shows the coupling ratio for on page 3. That’s why there is no coupling information listed for part ZB1200-DEC.

Hi Steve,
Thank you for your response.
I understand that the ZB1200-DE transformer is a balun and the impedance ratio between primary and secondary windings is 1:1.
I’m used to a standard where coupled windings are marked by placing a dot on one end of each of the windings in a way that describes orientation of voltage vectors induced by current flow in one of them.
This method is very useful in figuring out how the device works, for example why the common mode choke attenuates common signal and passes through the differential component.
This method is not applied to the ZB1200-DE schematic, winding between pins 3 and 6 has dots on both sides and the other two windings have none.
What is the meaning of the marking shown on the ZB1200-DE schematic?


Hi Steve,
I wanted to add few comments to my previous reply.
I think that the following might be true for an ideal component:

  • all 3 windings have the same inductance,
    ** perfect mutual coupling between windings 3-6 and 1-4,
    *** in my way of marking, the windings dots would be placed on the left end of windings 3-6 and 1-4,
    **** no coupling between winding 1-6 and the other two windings.
    I also presume that pin number 1 is marked with a dot, as shown on the balun image on page 1 of the datasheets.
    Please let me know your thoughts.


I’m not sure of the reasoning behind the dots on primary and secondary side and perhaps someone with more information on this can provide insight. Also, you are correct that pin 1 is marked with an indicator dot .