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Tolerances and Classification in Bill of Material of CC1200 Reference Design

Matthias May
Prodigy 140 points

While choosing parts for a custom CC1200-based radio module we had some questions regarding the bill of material of the reference design (http://www.ti.com/lit/pdf/tidr180 , http://www.ti.com/lit/pdf/tidr181) since some parts are not available or very expensive at our distributor.

Is it possible to replace some of the NP0 or similar classes caps with X7R/X5R with same tolerances or is the temperature-compensation of the NP0 class always required if NP0 is mentioned?

For example C231 is quite expensive at our distributor if you select the stated class (U2J), however, because we accidently ordered the wrong package, we found out that at least basic transmission between two chips on a desk works even without the C231. So now we wonder if a regular X7R/X5R would suffice.

Concerning the inductors, how do you choose the right inductor as there are much more properties like the Q factor, self-resonance that are not specified by the BOM? Are there some guidelines on how to determine the required minimum values?

In the RF circuitry like the balun or matching network, do you have to consider maximum current or voltage or are they always below the current/voltage properties of standard components?

Best regards,

Matthias

  • 0
    TI__Mastermind 29560 points

    Hi Mattias,

    For the capacitor C231, a reference of 1.5 nF is required for the operating temperature range. If you have a reduced temperature range and providing the capacitance is within the tolerances specified for the equivalent NPO capacitance reference then it should be OK.

    ML inductors can be used instead of WW inductors.

    Regards, Richard

  • 0
    TI__Mastermind 27145 points

    Hi,

    X7R/X5R are less stable componets when compared to NPO. X7R/X5R can be used for Couping/Blocking, decouping applications. NPOs are required in Filters and matching circuits due to their high stability.

    C231 is required in the circuit. It  is used in the loop filter and it will affect the phase noise performance. You can substitutute but it will affect the performance. So, it is a trade off between cost and performance.

    Regarding Inductors, you can use the equivalents to the inductors mentioned in our BOM. Refer to the Murata data sheet for LQW series inductors for specs.

    In the RF circuitry, the voltage will be very less . So, you can use low voltage rating components.

    Thanks,

    PM

  • 0 in reply to PM
    Prodigy 140 points

    Hi,

    thank you very much for your answers.

    Would it be possible so substitude C231 with a 0603 package? Availability and pricing is a lot better, however, according application notes and rf guidelines, 0603 should be avoided due to higher parasitic effects than 0402. Would you rate the C321 as too cricitial to be replaced by 0603 or is that an acceptable option?


    Best regards,


    Matthias May

  • 0 in reply to Matthias May
    TI__Mastermind 27145 points

    Hi,

    You can try 0603 on few boards and evaluate the RF performance of the board. If it is well within the specified limits then you can use it in the production. 

    Thanks,

    PM