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LMX2492 14GHz Output VCO-circuit

cafain
Mastermind 6365 points
Other Parts Discussed in Thread: LMX2492, LMX2492EVM, LM6211

Hi

General VCO I know needs more than 10V of voltage at 14GHz.

But Vcp of LMX2492 is Vcc (min) and 5.25V (max).

Vcc (for example, 3.3V) is low, so VCO of 14GHz can't be driven.

Do you know VCO where 14GHz can be output in LM2492?

If the circuit which amplifies the voltage of Vcp again is necessary, please tell me the circuit.

Best regards

  • 0
    TI__Expert 7855 points

    Hi Cafain,

    MACOM has VCO's that cover 14 GHz, look at MAOC-011027


    weblink:

    And you are correct, the tuning voltage for 14 GHz would be higher than the charge pump supply and you do need to use an active loop filter. Take a look at the users guide for LMX2492EVM page 12:

    This active filter uses an LM6211 which can bring your Vtune range up to 24V. It is a commonly used part in our designs, and the datasheet has more information on its application with PLLs.

    Regards,

    Brian Wang

  • 0
    TI__Expert 5370 points

    The LMX2492 has a PLL with a 5 V charge pump. This is already providing more range than 3.3 V and can save circuiry in some cases. We understand that this range does NOT cover all VCO out there.

     The search for a good integrated VCO can be a challenge. Depending on your application, you might want to make certain tradeoff and tuning range and voltage might be one of them. There are several vendors with excellent product however Ti is not one of them.

    As for a circuit, you should be looking for an op-amp to make an active loop filter. There is a significant amount of literature on the topic such as this one from university:

    users.ece.gatech.edu/~rincon/research/gtac/gtac_f3c.pdf

    Regards,
    Simon.