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LMK03328: PLLatinum simulation with LMK03328

Hirotaka Matsumoto
Guru 27585 points
Part Number: LMK03328
Other Parts Discussed in Thread: LMH1983

Hi all

Would you mind if we ask PLLatinum simulation with LMK03328?

Our customer will use LMK0328 and customer's configureation as follows;
<Customer's configuration>
LMH1983->27MHz->LMK03328->148.35MHz->FPGA

We simulated phase noise using PLLatinum.

1. Input phase noise from LMH1983
We refered to Figure 2. CLKout1 Phase Noise on the LMH1983's datasheet.

Offset frequency      Phase noise
100Hz                      -115.0dB
1000Hz                    -125.0dB
10000Hz                  -135.0dB
100000Hz                -146.0dB
1000000Hz              -150.0dB

2. We inserted these Phase noises at PLLatinum using .txt file.(We also attach .sim data for PLLatinum)

Fullscreen 6177.20200826_LMK03328_insert phase noise.txt Download 
100	-115.0
1000	-125.0
10000	-135.0
100000	-146.0
1000000	-150.0

(We compress the .sim file with .zip. Because the forum can't accept .sim file.)
20200826_LMK03328.zip

3. As the result, the phase noise at each offsets get worse 10dB.

If our procedure is not correct, could you give us advice?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Guru** 111690 points

    Hi Matsumoto-san,

    It is due to the phase noise of the 27MHz reference.

    See below the phase noise of the reference at 27MHz and at 148.5MHz. The phase noise at 27MHz will appear to be higher at higher frequency. The scaling factor is equal to 20log(new freq/existing freq). 

    Offset PN@27MHz PN@148.5MHz
    100 -115 -100.2015243
    1000 -125 -110.2015243
    10000 -135 -120.2015243
    100000 -146 -131.2015243
    1000000 -150 -135.2015243

    In this case, the overall PLL phase noise get degraded by this reference clock noise. You need a much better phase noise 27MHz VCXO. 

  • 0 in reply to Noel Fung
    Guru 27585 points

    Noel san

    Thank you so much for your reply!
    Compared with LMH1983's CLKOUT2, there is a little difference between LMH1983+LMK03328 and LMH1983's CLKOUT2.

    LMH1983+LMK03328 : -131.2015243dB@100kHz offset
    LMH1983's CLKOUT2 : -129dB@100kHz offset




    So, with LMH1983+LMK03328 combination, in order to improve phase noise at offset 100kHz, we have to choice good VCXO of LMH1983 and loopfilter setting?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Guru** 111690 points

    Hi Matsumoto-san,

    That is correct, because 100kHz offset phase noise is now dominated by the 27MHz clock source. 

    lane.boyd@ti.com