LMX2582: Random phase shift when calibrated

Alexey Faynburd

Part Number: LMX2582
Other Parts Discussed in Thread: LMX2594, LMX2820

Hi,

we employ frequency scan in our application. Every time the synthesizer calibrates frequency, it's phase randomly shifts (180, 120, 90 degrees depending on frequency). There is even no need to change the frequency, just calibrate anew.

It is a problem for us, as we measure the signal phase afterwards.

Why is this happening? And how can we get rid of it (or at the vey least predict the shift)?

Thank you,

Alexey

4 months ago

0 vicente flores prado 4 months ago

TI__Genius 13561 points

Hi Alexey,
Given there is no phase sync mode for this device, you have a total of N possible phases where N is your channel divider value. This phase will vary every time you power cycle or do a VCO calibration - thus the behavior you describe is expected. If you wish to have deterministic phase every time you power cycle or do a VCO calibration you require a device that supports phase sync such as LMX2594, LMX2820, etc.

Regards,

Vicente