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How to measure PLL's lock time?

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siboy

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pll lock time

The chip is a tranceiver, the pll's loop filter ans VCO is in the chip. I can only measure the PA's transmiting spectrum, or I can measure the receiver's leaking spectrum. So how can I measure the PLL's lock time ? (The simulated lock time is about 90us)
Thanks!
 

pll lock time measurement

That's why you design test modes into integrated transceivers, so you can bring test points out. You'll need to dig into the details of the IC to figure out how to do this. You may be able to do this from the transmitter port, but you need to look at the what happens in the transmit chain after the VCO, to make sure you actually are measuring the VCO power up, as opposed to the VCO power up, plus gain stages turning on.

Dave
 

phase locked loop lock time

In addition, PLL locked state doesn't necessarily guarantee the momentary VCO frequency to keep the regulation limits during transitions. particularly PA ramp-up. So it's meaningful to observe VCO frequency with final application mode and timing.
 

how to measure pll

Thank you!
I means can I use spectrum analyzer to measure this? And how to do it ? Is it accurate? The minmum sweep time of my spectrum analyzer is 50ms.
 

pll analyzser

No, usual slow scanning analyzers can't resolve PLL lock transients. The VCO control voltage is a better indicator for momentary frequency. If the frequency is sufficient low to be acquired by a DSO (e.g. < 1GHz), a precise high resolution frequency measurement can be achieved by digital signal processing.
 

pll locktime measure

First possibility is to use a dedicated instrument such as Agileng signal source analizer. It has a specific test mode to measure freq vs time.

Another good option is to use a spectrum analizer with FM demod option. Setting the spectrum freq at final PLL value, just trigger properly at the correct event, you'll see when the signal enter the receiving range of the demod.

Mazz
 

pll lock issue

Come on guys! How about some basice questions first. A PLL for an FSK system will have a different meaning of "lock time" than a QAM system! Why don't we get some more detailed info about what the system is from the original poster.

You can measure lock time externaly, depending on if you can turn off the modulation for such a test, for instance.
 

measure locking time

It's possible to measure lock-time by aid of an oscilloscope by triggerig single shot.If you use EN signal of PLL to trigger the sweep of an oscilloscope which should have trace memory option, you can check roughly lock-time on Vtune voltage.
 

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