• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 16 subscribers
  • Views 283 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CC2500: Crystal Selection

Dave Burlington
Prodigy 10 points
Part Number: CC2500

We have been making a board with the CC2500RGP on it for over 15 years and due to a limited supply of crystals we crossed our crystal to another one and now our radios are not working. I have checked everything on the scope and the waveform from the crystal looks good but the devices can not communicate. I am at a loss now on what to do and I have hundreds of boards with this new crystal and can not get the old one. Can you please review the data sheets and see if you can see something I am missing? thank you!


Old Crystal Part #NX3225SA-26.000000MHZ-G4

New Crystal Part #ABM8-26.000MHZ-10-E1U-T


The only difference I could see in the datasheets was the Shunt Capacitance went from 1.22pF to 3.0pF

NEW XTAL:

I

OLD XTAL:

 

Attached is Schematic for design reference:

At this point any insight or help is appreciated. 

  • 0
    TI__Guru**** 168357 points

    Hi,

    At first glance I don't see any significant differences between the two parts, but indeed the shunt and the load capacitances are different. Did you compensate for the higher load capacitance on the Abracon part?

    Note: I am using the datasheets on the links below:

    https://media.digikey.com/pdf/Data%20Sheets/NDK%20PDFs/NX3225SA-26.000000MHz-G4.pdf

    https://abracon.com/Resonators/abm8.pdf

    Hope this helps,

    Rafael

  • 0
    Prodigy 10 points

    The specific part from Abracon I ordered has same load capacitance as the NDK one. But just to validate it, I recalculated the capacitors and installed several variations of caps on the boards going up and down from the exact required caps. Unfortunately all the combinations I tried also failed.

    In reaching out to Abracon directly and they suggested I use a high frequency counter to validate the ppm of the crystal and make sure it’s not missing pulses. They said it’s possible these crystals are bad. Apparently my oscilloscope won’t capture this. The high frequency counter I have does not seem to be able to count the pulses on the crystal instead when I probe the crystals it appears the extra load stops the oscillations. Any suggestions here would be nice too. 

    Thanks

  • 0 in reply to Dave Burlington
    TI__Guru**** 168357 points

    Hi,

    Thanks for the additional information. I will consult with other colleagues to see if they could have additional insights.

    Regards,

    Rafael