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Original question:

CC1352P: RF Port Impedances

CC1352P: RF Port impedance required in the data-sheet.

James A.
Prodigy 105 points
Part Number: CC1352P
As a complete datasheet, the RF port’s impedance must be provided by the manufacturer. This is one of the essential design parameters for any RF device. This is extremely important as copying the reference design would just not work for some (and it is just wrong to copy a design, but let’s not get into that!) 1- The reference design is using components for 918MHz operation. I need to design the circuit for a different band. 2- Components used in the reference design are tiny 0201. For my application at lower frequencies I wish to use 0402 components so they are more manageable. 3- Reference design source files are provided in a software that I can not import into my software without the Original software installed. Therefore, can not just blindly copy a reference design. The port impedance is definitely a must have on the data-sheet for any RF device. I have worked out the impedance by reverse-engineering the reference design, but that is only applicable at 918MHz and at the mercy of selected component values. PS: Every reference design of the CCxxxx devices that I have seen, seems like produced by people with not much RF design knowledge or practise, which makes me sad :-(
  • 0
    TI__Mastermind 27145 points

    Hi,

    Please refer to the Application Note SWRA640 for Impedance info. The following is the Link.

    Thanks,

    PM

  • 0
    TI__Mastermind 33160 points

    Hi James,

    Agree that the RF port impedance is one important parameter in a reference design. This is why we specify it in the documentation. Please refer to the application note: CC13xx/CC26xx Hardware Configuration and PCB Design Considerations: http://www.ti.com.cn/cn/lit/an/swra640b/swra640b.pdf. Chapter 8 contains the optimum load impedance.

    However, our recommendation is to still copy the reference design since custom designs that simply match to a conjugate match at a single frequency will not give the best performance. The reference design is based upon simulations, load-pull, load-source and regulatory measurements. If you choose to tweek a design purely based upon simulations then the performance will not be optimized. 

    0201 components. The main reason for the industry to use this size of passives is mainly due to the directives from major passive suppliers such as Murata that do not recommend many 0402 sized components in new designs. We have used 0402 for many years as a standard size and due to the recommendations from Murata we have switched from 0402 to 0201. From a RF perspective, using 0201 has many advantages compared to 0402. 

    The CCxxxx reference designs are produced by various TI RF support teams around the world that have RF experience from many different universities/companies; stating that every reference design is produced by non-RF experienced engineers is an interesting and unjust comment. 

  • 0 in reply to RGW
    Prodigy 105 points
    Thank you for your swift response. A couple of issues are remaining: 1- The "swra604b.pdf" document references to a "LAUNCHXL-CC1352P-4" design document "swrc352" which is non-existent at this point of time. 2- The impedance of the RF port is not given for the whole range of frequencies that the device can operate in (433MHz ... 930MHz). Impedance only at 898MHz is provided for the Sub-GHz port. 3- The datasheet must provide all essential data without the need to search other documents for values, such as RF port impedance. It's just too important to be left out of the datasheet!
  • 0 in reply to James A.
    TI__Mastermind 33160 points

    The reference design is copied by 99 % of customers and this is the quickest way to finalize and optimize the design.

    At 433 MHz, the high output power is restricted by national regulations (typically 10 dBm_max). The high power PA port is mostly used for 868/915 MHz and 2.4 GHz. 

    Which regulations are you targeting to pass ?

    Which frequency band and maximum output power do you require ?

    Which PHY ?

    Regards,

       Richard