• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 22 subscribers
  • Views 330 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2571: Calibration schedule

Alex Strelbytskyy
Expert 1980 points

Part Number: LMX2571

Hello,

What is the time frame for the auto-calibration after starting synthesizer (with set FCAL_EN=1 in register R0)? When auto-calibration starts and when it is completed? What other calibration/RF activities are expected after that? Is calibration completed when synthesizer's LD is high?

Synthesizer's RF signal is being amplified by external PA on our board. We see some noise at antenna connector (~55kHz aside) when device is switching Tx-Rx.., that noise is initiated from synthesizer. Cold it be caused by some unexpected calibration or some other synthesizer's activity?

Thank you,

Alex 

  • 0
    TI__Guru** 121130 points

    Hi Alex,

    The calibration will start after R0 is programmed. The calibration time depends on the OSCin frequency. Datasheet has a number of 140µs which is the calibration time taken for the VCO to change from the lowest to the highest frequency, when the OSCin frequency is 100MHz. A lower OSCin frequency will increase the calibration time.

    Total frequency switching time is equal to the VCO calibration time + analog PLL lock time. PLL lock time depends on the loop bandwidth. You can use PLLatinum Sim to make an estimation. 

    In your plot, were you saying that the PA was always ON but you were toggling the synthesizer between TX and RX? Could you share you register configuration for both TX and RX? BTW, what is the OSCin frequency?