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LMX2571: Lock detection

Part Number: LMX2571

Question for LMX2571 lock detection.


Lock detect changes from L to H when frequency is changed in a high temperature environment (over 60°C)
On the other hand, it becomes L in about 1ms after turning H, and it becomes unlocked.
When fout was observed with a spectrum analyzer, the frequency was set
Frequency. Symptom occurs when internal VCO switching occurs
It seems to be awake.
VCO_SEL_STRT in R46 is set to Disabled.

① Why is it unlocked
② proposed countermeasures
I would like to ask you to teach us.

  • Hi Murayama-san,

    Could you provide your PLL configuration? How did you change the frequency, do you have a programming sequence?

  • Sorry Noel. I missed the data. Could you review below?

  • PLL Configulation is as attached.

    OSCiin = 115.2 MHz
    Pre-divider = 1
    MULT = 1
    Post-divider = 1
    Prescaler = 2
    
    External loop filter
    100pF
    220ohm + 22nF
    
    Data sent after power up
    3C A0 00
    3A 8C 00
    35 78 06
    2E 00 1A
    29 00 08
    28 08 1C
    27 11 FB
    23 00 22
    01
    18 00 10
    17 01 00
    16 85 81
    15 01
    14 30 28
    13 FF
    FF 12 00 00 00
    11 FF 00
    08 00
    00 00
    00 00 00 00 43
    17 01 00 00
    10 43
    17 01 40
    17 03 44
    16 85 21
    14 30 15
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    13 FF FF FF 12 C7 1C 11 FF 24 00 10 43 00 42 00 43 17 03 44 16 85 21 14 30 15 13 FF FF FF FF FF FF FF FF 12 71 C7 11 FF 5D 00 43 Data sent when changing frequency
    18 04 10
    17 03 44
    16 86 61
    14 30 16
    13 FF FF FF
    12 55 11
    FF A9
    00 43

  • Hi Taku-san,

    Thank you for the configuration. Noel is currently on travel but will reply to you when he is available.

    Best,

    Evan Su

  • Hi Murayama-san,

    What are the VCO frequencies? I am not able to get the VCO frequencies from the text file.