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Glitches at demodulated output of PLL and Voltage regulator

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emax0198

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PLL and Votage regulator

I am using MC145170 PLL frequency synthesizer for a receiver design that uses MAX883 voltahe regulator. The problem is that I am experiencing glitches at the demodulated output. Could it be the voltage regulator noise that is cauing the problem.

MAX883 data sheet says that the regulator introduces 250 micro volt RMS output noise. I am using the PLL at 61 MHz for a freqency range of 0.98 MHz with 50 channels (20KHz spacing).
 

Re: PLL and Votage regulator

Did you put a spectrum analyzer on the PLL's VCO RF output to see what the spurious and phase noise look like?
 

Re: PLL and Votage regulator

Wow- that's an old PLL chip. I doubt the regulator is the problem. I don't know the noise rejection of the power supply pin of this PLL but even if its poor, the noise of the voltage regulator will show up as increased phase noise, not glitches. I think you have other problem. Have you looked at the locked VCO and is the RF carrier clean or is it glitching. You may not have the PLL correctly designed.
 

PLL and Votage regulator

I think maybe the pll doesn't work properly.
 

Re: PLL and Votage regulator

i think its problem of locking
 

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