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LMK61E2: Best option of Programmable Clock for TIDA-00626 Reference Design

JATIN WANJARI
Prodigy 10 points
Part Number: LMK61E2
Other Parts Discussed in Thread: TIDA-00626, , LMK61E07, LMK61E08, LMX2592

Dear Team TI,

For TIDA-00626 Reference Design, which is the best choice of programmable clock from following:

1. LMK61E2 : Jitter: 90 fs RMS Typical fOUT > 100 MHz and stability: +/-50ppm over 10 years

2. LMK61E07 : Jitter: 90 fs RMS Typical fOUT > 100 MHz and stability: +/-25ppm over 5 years at 40deg Celsius

3. LMK61E08 : Jitter: 90 fs RMS Typical fOUT > 100 MHz and stability: +/-25ppm over 5 years at 40deg Celsius

Also, using lower logic voltages for I2C and SPI interface can reduce the leakage spurs from programmable oscillator and LMX2592 respectively at the output port of LMX2592?

  • 0
    TI__Expert 7800 points

    Hi Jatin, 

    The TIDA-00626 reference design uses LMK61E2 which has a different footprint compared to LMK61E07 and LMK61E08, so if you are using the gerber and PCB files from the reference design you will need to use LMK61E2.

    LMK61E2:

    LMK61E07/E08:

    If you are creating your own PCB files and can choose a new footprint, LMK61E07/E08 have better frequency stability compared to LMK61E2, but besides that their performance is identical. 

    For your 2nd question, I don't believe the I2C and SPI interfaces should have any significant impact on spurs. If this is a concern, you could unplug the I2C and SPI lines after you are done programming the devices. 

    Regards, 

    Connor 

  • 0 in reply to Connor Lewis
    Prodigy 10 points

    Dear Connor,

    Thanks for your suggestion.

    Is there any data available of LMK61E07/08 stability over 10 years or can we predict their stability over year using crystal parameter used inside these oscillator?

    Thanks

  • +1 in reply to JATIN WANJARI
    TI__Expert 7800 points

    Hi Jatin, 

    Unfortunately I don't think we have that data available. I believe the LMK61E07/E08 frequency stability metrics come directly from the internal crystal frequency tolerance, and it is measured differently compared to LMK61E2 since these devices use different crystals with different test specifications. Is 25 ppm stability over temperature, supply voltage, and 10 years of aging a must-have feature for your application?

    Regards, 

    Connor 

  • 0 in reply to Connor Lewis
    Prodigy 10 points

    Dear Connor,

    Thanks for the info.

    I'm designing a CW signal generator using LMX2592 based on TIDA-00626 design, for which I need to select among best possible choices of components which can be used as LO source/IF source for my application.

    As per your suggestion, I will go LMK61E07.

    Thanks