Phase Lock Loop using IC 565

The LM-565 and LM-565C are general purpose phase locked loops containing a stable, highly linear voltage controlled oscillator for low distortion FM demodulation, and a double balanced phase detector with good carrier suppression. The VCO frequency is set with an external resistor and capacitor,and a tuning range of 10:1 can be obtained with the same capacitor.

The characteristics of the closed loop system—bandwidth, response speed, capture and pull in range—may be adjusted over a wide range with an external resistor and capacitor. The loop may be broken between the VCO and the phase detector for insertion of a digital frequency divider to obtain frequency multiplication.

The LM-565 is specified for operation over the −55°C to +125°C military temperature range. The LM565C is specified for operation over the 0°C to +70°C temperature range.
PLL consist of phase detector, an amplifier, low pass filter and VCO. The phase locked feedback loop is not internally connected. Therefore it is necessary to connect the output of VCO (Pin no 4) to the input of phase comparator (Pin 5).

The free running frequency of PLL is determined by the external connected components RT and CT. This formula is

The values of RT and CT are adjusted such that the red running frequency will be at the centre of the input frequency rage. The value of RT is restricted from 2K OHMS to 30 K OHMS. But a capacitor can have any value. A capacitor (CF) connected between pin 7 and the supply voltage (pin 10) forms a LPF. The value of filter capacitor should be large enough to eliminate possible oscillations in the VCO voltage

Leave a Reply

Your email address will not be published. Required fields are marked *