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AWR2243: there is spurious when we use TCXO

xu qingjie
Intellectual 320 points
Part Number: AWR2243

Hi supporter:

We use 40MHz  TCXO ( KDS DSB321SDN  ) to replace XO to avoid AWR2243 Device Errata ANA#18B Spurs Caused due to Digital Activity Coupling to XTAL.

But there is spurs about 1.2MHZ with TXCO,we can notice the spurs on the RD image.And it`s clear with XO.

We have checked TCXO Vcc ripple.and it is clean.

the below picture shows wave form of TCXO.and the Vp-p is about 0.93V

Do you have  any ssuggestion ？

thanks~

  • 0
    TI__Guru 58035 points

    Hello ,

    While using the TCXO have you pulled the XTAL_M pin to Gnd? Is there any 1.2Mhz clock in the system? like is the power supply a switching regulator with 1.2Mhz switching freqeuncy?

    Regards,

    Vivek

  • 0 in reply to Vivek Dham
    Intellectual 320 points

    Hi vivek；

    I have pulled XTAL_M pin to GND.  We use PMIC 87524P and the switch frequency is 4MHz.

    It`s strange and I have no idea about this. Have TI tried TCXO？Can you offer the material model for us to try？

    thanks

  • 0 in reply to xu qingjie
    TI__Guru 58035 points

    Hello Xu,

    We have tested the TCXO mode by feeding the clock from an external equipment. I would like to understand the reason you suspect the TCXO operation. Do you have another replica of the HW using the xtal where you dont see the issue?  Or have you fed external clock from an equipment instead of TCXO to see if the issue goes away?

    regards,
    Vivek

  • 0 in reply to Vivek Dham
    Intellectual 320 points

    Hello Vivek；

    There is not spur when we use xtal.

    Did you mean use a signal generator to fed the clock? And generate 40MHz sine wave ?

    thanks

  • 0 in reply to xu qingjie
    TI__Guru 58035 points

    Hello,

    Do you mean on the same board you have option to use TCXO or XTAL and XTAL does not show the spur? In that case the TCXO clk itself might have the spur. Have you measured the phase noise of the TCXO o/p ? You could feed 40Mhz sin/square wave using external equipment also and see if the spur changes.

    regards,
    Vivek