elisemark
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in my circuit design I am sending an oscillator output signal into a CD4046 PLL, the oscillator frequency is around 850KHz, now I calculated all the PLL parameters well and it did work for a while then now I have a nice square wave(@310KHz free running) as soon as I connect the oscillator signal then I loose the VCO signal ( 0 volts) then after a few seconds the VCO signal becomes a flat DC signal at around 4.5V.
1. any idea why this is happening
2. also should I expect the VCO value at pin 4 of the CD4046 to be near 850KHz with no signal input connected ( free running VCO) ? R=10K and C=470pF.
the loop filter is designed with a cut off frequency just below 50Hz.
Thanks for any feedback
1. any idea why this is happening
2. also should I expect the VCO value at pin 4 of the CD4046 to be near 850KHz with no signal input connected ( free running VCO) ? R=10K and C=470pF.
the loop filter is designed with a cut off frequency just below 50Hz.
Thanks for any feedback