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LMX2572: VCO lock condition under temperature change

Koshi Ninomiya
Expert 5045 points
Part Number: LMX2572

Dear Team,

My customer is evaluating LMX2572 and has some questions about VCO of it.

Q1. Once the VCO of LMX2572 has locked, it never unlocks under recommended operating range of  ambient temperature from -40 degC to +85 degC, right?
       For example, once the VCO has locked under Ta=-40 degC, it never unlocks when Ta becomes +85 degC, right?
       To know that characteristic, which parameter in the LMX2572 datasheet should they refer?

Q2. How is the VCO frequency selected?
       Is the VCO frequency is selected based on only output frequency setting? Or are there other factors?

Q3. Could the VOC frequency vary by ambient temperature change?

Thank you.

Best Regards,

Koshi Ninomiya

  • 0
    TI__Guru* 98190 points

    Hi Ninomiya-san,

    Q1, That is correct. This data is available in the Electrical Characteristics section. It is called Allowable Temperature Drift.

    Q2, When R0 is programmed, the chip will initiate a VCO calibration routine. This routine will select the correct VCO core (we have six VCO cores), the best bands (we called this capcode) and amplitude (we called this DACISET).

    Q3. Yes, VCO frequency will drift over temperature, that is why it needs a PLL to make it stays at a constant frequency.