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Original question:

LAUNCHXL-CC13-90: Schematic explanation

LAUNCHXL-CC13-90: Reference Design Schematic Question

Yash Bhat
Prodigy 30 points
Part Number: LAUNCHXL-CC13-90
Other Parts Discussed in Thread: CC1190, CC1310

Hello,

I'm working on a design involving the CC1310 and CC1190 and I'm referencing the CC1310-CC1190 Reference Design US schematics. I've referenced a few resources, including www.ti.com/.../swra542, using CC1190 with CC13xx, and www.ti.com/.../swra640g, the CC13xx hardware design guide, and had some questions about the purpose of some components. I'm adding what I think I know about some of them, please correct me if I'm wrong?

What is L24/C25 used for? I see that C212/L27 is a notch filter for harmonics, but I'm not sure why C24 is left unfilled in the current schematic? I also wanted to confirm that impedance entering the SMA connector after L24 is matched to 50 Ohms, right? I believe A2/A3 are used to match impedance for the PCB antenna included in the development board. I see that C214/L26 are used to match impedance to LNA_IN pin.

I see that C27/C28/C29 are decoupling capacitors for CC1190 supply, but what do L131/C131 and L161/C161 do? Filters against harmonics in power supply? If so why is R151 sufficient for VDD_PA2? From the pin table in the CC1190 datasheet it seems all three VDD pins serve the same purpose, so why would they have different LC values?

Thanks for any input, I appreciate it!

  • 0
    TI__Genius 12285 points

    Hi,

    • L24/C25 form part of the LC low-pass filter network (that also performs an impedance matching function).
    • C24 is mounted for the EU version of the design to provide additional filtering of the 2nd harmonic to pass ETSI regulations. It is not required for the US BOM.
    • Yes, the impedance entering the SMA connector after L24 is 50 Ohms.
    • That is correct, but R151 is included for stability reasons; it was found to be sufficient through lab testing. This can be dependent on the PCB layout, and additionally those pins are in proximity to other pins on the CC1190 itself (so they are not guaranteed to require the exact same decoupling/filtering networks). 

    Regards,

    Zack