Monolithic Phase Locked Loops (PLL IC 565):
The important electrical characteristics of the 565 PLL are,
· Operating frequency range: 0.001Hz to 500 Khz.
· Operating voltage range: ±6 to ±12v
· Input level required for tracking: 10mv rms min to 3 Vpp max
· Input impedance: 10 K ohms typically.
· Output sink current: 1mA
· Output source current: 10 Ma
The center frequency of the PLL is determined by the free running frequency of the VCO, which is given by
fOUT = 1.2/ 4R1C1
where R1&C1 are an external resistor & a capacitor connected to pins 8 & 9.
· The VCO free-running frequency fOUT is adjusted externally with R1 & C1 to be at the center of the input frequency range.
· C1 can be any value; R1 must have a value between 2 k ohms and 20 K ohms.
· Capacitor C2 connected between 7 & +V.
· The filter capacitor C2 should be large enough to eliminate variations in the demodulated output voltage in order to stabilize the VCO frequency.
The lock range fL & capture range fc of PLL is given by,
∆fL= ±7.8 fout/ V Hz
Where fOUT = free running frequency of VCO (Hz)
V = (+Vcc)-(-Vcc) volts
∆fC= ±[ ∆fL/(2Π)(3.6)(103)C2 ]½