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DAC5681: Output Signal Coupling

Other Parts Discussed in Thread: DAC5681


I'm designing a board with the DAC DAC5681. Reading the user guide in which there's the electrical drawing of the EVB, I need the balun transformer at the DAC output to have a single-ended 50 OHm net. This is also the default configuration in your EVB, because you use the output connector J1 (IOUTB2), see the attached file.

Could you tell me what output coupling has the DAC output using the balun transformer with the default configuration?

I look forward to hearing from you.

Best Regards,

Simona Mazzocchi  



  • Simona,

    I'm not sure I understand the question completely - I'm assuming you wish to know the effective AC load as seen by the DAC output pins?

    The circuit is setup in a manner which expects test equipment which is terminated with 50 ohms at the output connector J1.  Through the 4:1 impedance ratio transformer T1, his will present 200 ohms AC impedance between pins 4 and 6 of T1.  However this is split in the middle so that there is 100 ohms between 4-5 and 100 ohms between 5-6 of T1.  This will be in parallel to the 100 ohms already present on each of the T1 pins 5 and 6.  The final result is the DAC IOUTB1 and IOUTB2 will see effectively 50 ohms impedance on each of the output pins.


  • Hi Ken,

    Thanks for your answer. 

    I would like to have a single-ended 50 Ohm net after the balun transfomer; from your answer I understand that the default configuration allows to have this net at the connector J1. 

    Could you tell me if the output signal at J1 (IOUTB2) has the AC coupling feature?

    I think it has it, but I would like to know your idea about it.

    I look forward to hearing from you.

    Best Regards,