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TRF370417: TRF370417

Part Number: TRF370417

Hello!

I'm going to interface the DAC38J84 to the TRF370417 I/Q modulator.

I've found an application note SLUA647A "Analog Interfacing Networks for DAC348x and Modulators" and there is an explanation of passive single-supply level translation interface at pages 7-8.

My question is:

1. What is a correct value of TRF370417 input baseband impedance - 5 kOhm (as it written in the TRF370417 datasheet) or 20 kOhm (as it written in the Table 1 of application note)?

2. In case there is a mistake in application note and the correct value is 5 kOhm, how does one re-calculate the R1 - R4 resistors values? Can you please provide the required equations?

 Thanks!

  • Hi Edward, 

    Check out this TI design : http://www.ti.com/tool/tida-00335 

    I think you'll find it very helpful.

    Regards,

    Abdallah

     

  • In reply to Abdallah Obidat:

    Hello, dear Abdallah,

    Thank you for your quick replay!
    It will help me with my second question regarding calculating the resistors values.

    But I still need an answer regarding my first question - what is a correct value of the TRF370417 input baseband impedance - 5kOhm or 20kOhm?

    Can you please check this issue?

    Thanks in advance!
    Edward
  • In reply to Edward Mirodin:

    I am looking into this.

  • In reply to Edward Mirodin:

    Hi Edward,

    The baseband input impedance could be treated as high impedance and is not absolutely necessary to complete your calculations, but including it will improve accuracy. It seems that the 5k resistance was the result of simulation, while the 20k value was determined empirically, and that the 20k value would be more accurate for your calculations. 

  • In reply to Abdallah Obidat:

    Hi Abdallah,

    Thank you for your answer.
    Now I can proceed with my design.

    Best regards,
    Edward

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