• TI Thinks Resolved

LMX2571: There are several MHz that cannot be locked

Expert 3440 points

Replies: 2

Views: 27

Part Number: LMX2571

Hi team,

The frequency that the customer needs to receive is 326M ~ 396M, and the frequency that the customer needs to send is 400 ~ 470M. However, after the register is configured, the transmit locking range is only 400-466M, and the receive frequency is only 326-392M. The register configuration has been modified EXTVCO_CP_GAIN,EXTVCO_CP_IUP and EXTVCO_CP_IDN and so on, but no matter how to change, the result is the same, there are several MHz can not be locked.

The external VCO is used. Some hardware information is as follows:

CV voltage range 0-5V (corresponding to receiving frequency 310M-410M, corresponding to transmitting frequency 390-485M), we need frequency corresponding to voltage 1-4V

Feedback loop Fin = -40dbm.

Best Regards,
Amy Luo

  • Hi Amy,

    Fin = -40dBm, isn't it a typo?

    What is the Vtune voltage at 326MHz, 392MHz, 400MHz, 466MHz?

    What is the supply voltage at VcpExt pin?

  • In reply to Noel Fung:

    Hi Noel,

    Thank you for your reply. The problem has been found. It's a hardware problem. It has nothing to do with LMX2571

    Best Regards,
    Amy Luo