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CC2530: CC2530 crystal selection

Andreas Nilsson1
Prodigy 20 points
Part Number: CC2530


Hi,

one thing that confuses me is the crystal specification parameters in the datasheet "SWRS081B –APRIL 2009–REVISED FEBRUARY 2011".

AFAIK, Cl is the load capacitance that a specific crystal is designed for. So when I choose a crystal, I need to combine it with two capacitors to meet its desired Cl, using the formula

Cl = (C1 * C2) / (C1 + C2) + Cstray

Therefore, it seems very strange to me that TI present a range for Cl from 10 to 16 pF. I've never seen this in other MCU datasheets.

However, the datasheet says "Measured on Texas Instruments CC2530 EM reference design with TA = 25°C and VDD = 3 V, unless otherwise noted".

But what would make more sense is to present the parasitic capacitance on the XTAL pins.

Am I totally wrong, or do you agree with me?

Best regards.

  • 0
    TI__Genius 15590 points

    Hi Andreas,

    I have forwarded your question to one of my colleagues. 

    Thanks,

    Alexis

  • 0 in reply to Alexis Crandall20
    TI__Mastermind 27145 points

    Hi,

    Yes, your formula is correct. Yes, you need to tune the Load Capacitor values for Frequency accuracy of the crystal.

    Please note that the Load Capacitance should be specified when the Crystal is used in a parallel mode.

    We recommend to use the Crystal which meets the specs mentioned in the data sheet ( SWRS018). 

    The statement "Measured on Texas Instruments CC2530 EM reference design with TA = 25°C and VDD = 3 V, unless otherwise noted" may not be applicable to all the specs mentioned for the crystal but for Start-up time and Power down guard times.

    Thanks,

    PM