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CC1312R: impedance

Part Number: CC1312R
Other Parts Discussed in Thread: CC1310

Tool/software:

What is the balanced low-import impedance of pins 1 (RF_P) and 2 (RF_N) of the CC1312R1F3RGZ?

  • Hi,

    What are you aiming to implement with the information?

    The optimum impedance depends, amongst other things, on the frequency band of operation/TX Output Power/voltage. Section 9 of SWRA640 (CC13xx/CC26xx Hardware Configuration and PCB Design Considerations): https://www.ti.com/lit/swra640 describes this in more detail.

    So, we are able to better help if we have some more information about your aims here.

    Regards,

    Zack

  • Thank you for your quick answer.

    Once the impedance was known, we thought of using a transformer to perform both impedance conversion and unbalanced conversion at the same time.

     

    https://www.ti.com/lit/swra640 have been confirmed.

     

    I'm thinking of using it in a single-ended way.

     

    According to the description of "2.3.2 Single-Ended TX Only", the impedance is written as "14-j20Ω".

     

    However, according to the description of "9 Optimum Load Impedance", "It changes with the configured output power level and is not

    linear."

    Also

    CC1310, CC1312

    • 863-928 MHz

    868 MHz target load impedance: 40 + j15 Ω

    • 2440 MHz target load impedance: 25 j10 Ω」

    There is also a description of.

     

    Does this mean that when used in a single-ended system, the impedance varies with frequency and transmission power, and is not uniquely determined?

  • Hi,

    Those target impedances have been removed in the latest revision of SWRA640 (Rev. H) precisely because it varies with specific conditions and performance requirements; please review Rev. H for a more detailed description. In short, at the time of writing there are many variables to consider when determining the optimum load/source impedance(s) and currently has been causing more confusion than it solves by including those target impedances in SWRA640 (as parameters such as device package size also must be accounted for).

    Additionally, we are currently working on improved single-ended designs so have not finalised these. The target impedances for differential and single-ended operation will differ, regardless.

    When you write "I'm thinking of using it in a single-ended way" and "we thought of using a transformer to perform both impedance conversion and unbalanced conversion at the same time": the specific planned mode operation matters here. If you are planning to operate the device in single-ended mode then a balun is unnecesary (and therefore so is a transformer), as filter/impedance transformation network(s) is/are what is required.

    For the frequency bands of operation that have reference designs (which already include 863-928 MHz and 2440 MHz), it is recommended to closely follow the reference designs.

    Regards,

    Zack