LMX2571: LMX locked error

Harry Ma

Part Number: LMX2571

Hi experts.
After the phase-locked loop locks the frequency, it will send out a lock signal. 
I wanna know for LMX2571, how much is the error between the actual output frequency and the ideal frequency, the PLL considers it locked?

over 3 years ago

0 Noel Fung over 3 years ago

TI__Guru** 108550 points

Hi Harry,

Lock detect does not check the output frequency, it will turn HIGH when VCO calibration is complete and the Vtune voltage is within a reasonable range.

0 Harry Ma over 3 years ago in reply to Noel Fung

TI__Intellectual 2660 points

Thanks Noel

How much is this reasonable rang?

+1 Noel Fung over 3 years ago in reply to Harry Ma

TI__Guru** 108550 points

Hi Harry,

This is done inside the chip, this range is proportional to Vtune but not equal to Vtune.

Please note, Vtune is not a fixed voltage, it will change according to temperature. As long as the PLL loop is locked, Vtune will stay at a steady voltage. If unlock, Vtune will usually be staying at either 0V or around 2.5V.

0 Harry Ma over 3 years ago in reply to Noel Fung

TI__Intellectual 2660 points

Thanks Noel

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LMX2571: LMX locked error