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LMX2434 / Different VCO is mounted on EVM

S.Satoshi
Guru 21675 points
Other Parts Discussed in Thread: LMX2434, LMX2430, LMX2433

Hi All,

Our customer ordered LMX2434EVAL to evaluate 4.8GHz VCO Frequency. I understand that the VCO which has frequency around 4.8GHz is needed to 4.8GHz VCO frequency directly, and so the BOM of LMX2434EVAL list VCO690-4790T. But the actual VCO mounted on EVM is not VCO690-4790T. It looks "CVCO55BH-4100-4300" as attached photo. I believe we can't generate 4.8GHz directly with this VCO. Please confirm it and give your comments.

http://www.crystek.com/home/vco/cvcodetail.aspx?pn=CVCO55BH-4100-4300

Please feel free to contact me directly for email address in my profile.

Best Regards,

Sonoki / Japan Disty

  • 0
    TI__Mastermind 27831 points

    Satosih-san,

    Indeed this is a different VCO.   We have a serious problem with VCO vendors obseleting VCOs or VCOs not being available, so we switched to these crystek VCOs that are available on digikey.  The correct BOM is as follows:

     

    LMX2434 Build Only

    PLL

    National Semiconductor

    LMX2434TM

    1

    U1

    VCO

    Crystek

    CVCO55BH-4100-4300

    1

    U2

    100 pF

    Kemet

    C0603C101J5GAC

    1

    C1_RF

    3.9 nF

    Kemet

    C0603C392J5GAC

    1

    C2_RF

    1 nF

    Kemet

    C0603C102J5GAC

    1

    C3_RF

    3.3 k

    Vishay/Dale

    CRCW06033K30JNEA

    1

    R2_RF

    680 ohm

    Vishay/Dale

    CRCW0603680RJNEA

    1

    R3_RF

     

     

    Parameter

    LMX2430

    LMX2433

    LMX2434

    VCO Frequency

    (MHz)

    1600 – 1675

    3200 - 3400

    4100 - 4300

    VCO Gain

    (MHz/V)

    32

    90

    100

    Charge Pump Gain (mA)

    4

    4

    4

    VCO Input Capacitance

    39

    22

    10

    Phase Detector Frequency (MHz)

    1

    1

    1

    OSCin Frequency (MHz)

    100

    100

    100

    Loop Bandwidth (kHz)

    27.9

    31.1

    49.0

    Phase Margin (deg)

    56.8

    59.6

    58.2

    Gamma

    0.57

    0.90

    1.23

    T3/T1 Ratio (%)

    220.8

    177.1

    213.5

    C1_LF (nF)

    0.18

    0.27

    0.1

    C2_LF (nF)

    6.8

    10

    3.9

    C3_LF (nF)

    1

    1

    1

    C4_LF (nF)

    Open

    Open

    Open

    R2_LF (Kohm)

    2.2

    1.8

    3.3

    R3_LF (Kohm)

    0.82

    0.82

    0.68

    R4_LF (Kohm)

    0

    0

    0
  • 0 in reply to Dean Banerjee
    Guru 21675 points
    Hi Dean-san,

    Thank you for your quick response. Do you know if an alternative VCO solution is available from VCO vendor? The difference footprint will be OK though the same footprint is needed to replace directly on EVM.

    Best Regards,
    Sonoki
  • 0 in reply to S.Satoshi
    TI__Mastermind 27831 points
    Sonoki-san,
    These Crystek VCOs were from Digikey. They share the same 0.5 x 0.5 inch footprint with Zcomm and RFMD, although I like Crystek because they are available on digikey and finding VCOs in stock is a challenge.
    If you change the VCO, then you might need to re-design the loop fiter as well. But why would you want to replace the VCO?
    REgards,Dean
  • 0 in reply to Dean Banerjee
    Guru 21675 points
    Hi Dean-san,

    Our customer want to replace the VCO because they need 4.8GHz VCO frequency. Do you know the replace parts from Zcomm and RFMD for VCO690-4790T?

    Best Regards,
    Sonoki
  • 0 in reply to S.Satoshi
    Guru 21675 points
    Hi Dean-san,

    This business is in under development phase so it's possible for cancel, but they bought two LMX2434EVALs to evaluate 4.8GHz VCO frequency because the user's guide state that it can be used with 4.8GHz. So I would like you to obtain and send the replacement part for VCO690-4790T from other vendor like Zcomm or RFMD. Please discuss this offline if you need. Please check my email in profile.


    Best Regards,
    Sonoki