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LMX2572: Fully-assisted VCO calibration, collected parameters does not work on production HW.

Henrik Omberg
Prodigy 20 points
Part Number: LMX2572

We have collected a set of parameters for fully assisted VCO calibration on a lab-setup using TI's development board.

When I test these parameters on our production HW the parameters does not give the expected frequency. Ex: setting 1000MHz give 992Mhz.

From this a make the assumption that the parameters depend on your HW, is this correct?

If I collect a new set of parameters on our production HW, will they work on all individuals?

One final question. Will the MUXOUT pin show LOCK when fully assisted VCO calibration is used? Or is this pin only used when FCAL_EN is set?

  • +1
    TI__Guru* 97910 points

    Hi Henrik,

    Due to part to part variation, we should not apply a "golden calibration data" to any device. We'd better create the look up table on each board and on each device. 

    No matter which LD_TYPE you have selected, LD will only assert when there is at least one calibration is complete. If we use full assist but never calibrate the device, we will get the device lock but LD will remain LOW. So in order to use LD in full assist mode, we should calibration the VCO at least once. For example, after a Vcc power up, we lock the device without any VCO assist. Then LD will turn HIGH. Now, we can put it in full assist mode, change frequency and LD will response to the actual lock status.