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CC2591 Impedance Design

Theng Hoo Koay
Prodigy 160 points
Other Parts Discussed in Thread: CC2591, CC2530, CC2520

Hi there,

My customer is using CC2591 in thier design and facing some issues on below. Hope to receive some advises to overcome it :

1) In the CC2591 datasheet (page 1), what is the impedance at the RF_N and RF_P ports? Is the impedance provided single ended or balanced? Is this impedance looking into the antenna or looking out?

 2) What is the impedance of the antenna port? If it is 50 ohms, why is a matching network required?

Any advise is much appreciated!

Thanks.

- Koay

  • 0
    Intellectual 445 points

    Hi Koay,

    Which radio is your customer using the CC2591 with? We highly recommend that they copy our reference designs (components, layout and board stack-up) for the various radios (CC2530/40, CC2520, etc)

    The reason we do not provide impedance values in the datasheet is that it can be slightly misleading since it's not only the impedance at the carrier frequency that's important, but also the impedances at the harmonic frequencies. Customers who design a network for a given 2.4GHz impedance can therefore still experience problems with output power and efficiency. That's why copying the right reference design is our clear recommendation.

    The matching network between the CC2591 pin 11 and the SMA antenna port is designed to provide a 50 ohm impedance at the antenna port.

    EWI

  • 0 in reply to Espen Wium
    Prodigy 160 points

    Hello EWI,

    Thanks for your reply.

    The transceiver that my customer using right now is Nordic nRF24L01P. Basically it doesn't have any problem during PP stage when when comes to production, it facing some issues on the impedance matching.

    Thanks.

    - Koay.

  • 0 in reply to Theng Hoo Koay
    TI__Mastermind 39860 points

    Your question has been answered on the community several times before. Recommendation is to do a search on E2E.

    Optimum load impedance is 13 ohm + small imaginary part (i.e. as seen from from ANT pin towards the antenna/50 ohm load). See http://e2e.ti.com/support/low_power_rf/f/155/p/153328/653936.aspx#653936, post dated Dec 19th 2011 by Tor-Inge