IC phase locked loops (PLL) are closed-loop frequency controls that are based on the phase difference between the input signal and the output signal of a controlled oscillator. An IC phase-locked loop generally consists of a phase detector, a loop filter, voltage controlled oscillator (VCO) and an amplifier.

There are several ways in which IC phase locked loops (PLL) function. An IC phase-locked loop is an electronic circuit which controls an oscillator and provides an output signal. This output signal should be capable of maintaining a constant phase angle with respect to the reference signal in the range of few Hz to many GHz.

A digital phase locked loop is comprised of a serial shift register that receives digital input, a local oscillator that gives clock pulse to the shift register, and a phase corrector circuit that produces a stable clock, which is in phase with received signal. A digital PLL chip can interface with more than one device. Some specifications of the frequency synthesizer digital PLL includes frequency range, output power and step size.

Types of IC Phase-locked Loops (PLL)

A digital phase locked loop circuit is used if the data and clock are to be sent together over the same cable because in this circuit the receiver separates the clock from the data received.

A digital PLL chip simplifies the clock design and increases reliability of the circuit in which it is present. A current loop driver kit is a type of phase locked loop circuit in which the phase detector is not present.

A current loop chip is a programmable chip and it can directly interface to the computer.

In an ADC phase locked loop, the analog signal is converted into the digital signal.

A synthesizer digital PLL is a type of frequency synthesizer, an electronic device that is capable of producing frequency coherent to a reference frequency.

Other IC phase locked loops (PLL) are commonly available. 

Applications

IC phase locked loops are used in many applications. Some examples include application in the communications field to lock the communication signals in their frequency range, frequency synthesizers, and signal regeneration. IC phase locked loops (PLL) should adhere to Institute of Electrical and Electronics Engineers (IEEE)  and other industry standards. 

Standards

SMD 5962-77050 - Microcircuit, linear, phase-locked loop system, monolithic silicon

SMD 5962-94664 - Microcircuit, digital, CMOS, micropower phase-locked loop system, monolithic silicon

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Texas Instruments