However, if there is an accident, a yellow caution flag is raised. This is analogous to the PLL in an unlocked state. The separation of the cars (a distance) corresponds to the phase difference between the two oscillating signals.ĭuring most of the race, each car is on its own and free to pass the other and lap the other. The number of laps per hour (a speed) corresponds to the frequency. Each lap corresponds to a complete cycle.

One represents the input frequency, the other the PLL's output voltage-controlled oscillator (VCO) frequency. Practical analogies Automobile race analogy Īs an analogy of a PLL, consider a race between two cars. 7.4 Implementing a digital phase-locked loop in software.Since a single integrated circuit can provide a complete phase-locked-loop building block, the technique is widely used in modern electronic devices, with output frequencies from a fraction of a hertz up to many gigahertz. They can be used to demodulate a signal, recover a signal from a noisy communication channel, generate a stable frequency at multiples of an input frequency ( frequency synthesis), or distribute precisely timed clock pulses in digital logic circuits such as microprocessors. Phase-locked loops are widely employed in radio, telecommunications, computers and other electronic applications.

These properties are used for computer clock synchronization, demodulation, and frequency synthesis. Consequently, in addition to synchronizing signals, a phase-locked loop can track an input frequency, or it can generate a frequency that is a multiple of the input frequency. Keeping the input and output phase in lock step also implies keeping the input and output frequencies the same.

The oscillator generates a periodic signal, and the phase detector compares the phase of that signal with the phase of the input periodic signal, adjusting the oscillator to keep the phases matched. There are several different types the simplest is an electronic circuit consisting of a variable frequency oscillator and a phase detector in a feedback loop. A phase-locked loop or phase lock loop ( PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal.

Clockgen pll setup download