Pll
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phase-locked loop def ini ti on
A phase-locked loop (PLL) is an electronic circuit with a voltage- or currentdriven oscillator that is constantly adjusted to match in phase (and thus lock on) the frequency of an input signal. In addition to stabilizing a particular communications channel
Design fundamentals
Figure 1. Feedback System
Figure 2. Phase locked loop Parameter Definition The Laplace Transform permits the representation of the time response f(t) of a system in the complex domain F(s). This response is twofold in nature in that it contains both transient and steady state solutions. Thus, all operating conditions are considered and evaluated. The Laplace transform is valid only for positive real time linear parameters;
thus, its use must be justified for the PLL which includes both linear and nonlinear functions. This justification is presented in Chapter Three of Phase Lock Techniques by Gardner. Using servo theory, the following relationships can be obtained.2
These parameters relate to the functions of a PLL as shown in Figure 2. The phase detector produces a voltage proportional to the phase difference between the signals qi and qo/N. This voltage upon filtering is used as the control signal for the VCO/VCM (VCM – Voltage Controlled Multivibrator). Since the VCO/VCM produces a frequency proportional to its input voltage, any time variant signal appearing on the control signal will frequency modulate the VCO/VCM. The output frequency is
From another source much simpler:
Outline 1•Basic PLL system 2•Basic circuit block 3–Phase detector 4•Analog mixer 5•Digital 3 state Phase Frequency Detector 6•Charge pump circuit 7–Filter 8–Voltage Controlled Oscillator 9•Pull-in process 0•System characteristics (frequency and time response) 10–With 1st order filter 11–With Lag-Lead filter 12•Delay Locked Loop 13•Clock recovery circuits 14•Frequency synthesizer
Application Area: 11.Internal clock generation in LSI locked to external clock 22.Frequency Synthesizer for communication systems 33.Clock recovery for communication systems and data storage systems 44.FM demodulation Frequency Synthesizer
Clock Recovery
PLL is a feedback system to match the input signal phase and the output signal phase. Through this process, frequencies of these signals become equal completely.
WAVEFORM IN PLL SYSTEM
Analog phase detector (mixer type)
3 state Phase Frequency Detector This 3 state phase detector is currently most widely used. Because it has a ability for frequency detect.
Dead Zone in PFD The most serious issue of PFD is dead zone at a small phase deviation. This causes a large jitter and a phase noise.
A phase-locked loop (PLL) is an electronic circuit with a voltage- or currentdriven oscillator that is constantly adjusted to match in phase (and thus lock on) the frequency of an input signal. In addition to stabilizing a particular communications channel
Design fundamentals
Figure 1. Feedback System
Figure 2. Phase locked loop Parameter Definition The Laplace Transform permits the representation of the time response f(t) of a system in the complex domain F(s). This response is twofold in nature in that it contains both transient and steady state solutions. Thus, all operating conditions are considered and evaluated. The Laplace transform is valid only for positive real time linear parameters;
thus, its use must be justified for the PLL which includes both linear and nonlinear functions. This justification is presented in Chapter Three of Phase Lock Techniques by Gardner. Using servo theory, the following relationships can be obtained.2
These parameters relate to the functions of a PLL as shown in Figure 2. The phase detector produces a voltage proportional to the phase difference between the signals qi and qo/N. This voltage upon filtering is used as the control signal for the VCO/VCM (VCM – Voltage Controlled Multivibrator). Since the VCO/VCM produces a frequency proportional to its input voltage, any time variant signal appearing on the control signal will frequency modulate the VCO/VCM. The output frequency is
From another source much simpler:
Outline 1•Basic PLL system 2•Basic circuit block 3–Phase detector 4•Analog mixer 5•Digital 3 state Phase Frequency Detector 6•Charge pump circuit 7–Filter 8–Voltage Controlled Oscillator 9•Pull-in process 0•System characteristics (frequency and time response) 10–With 1st order filter 11–With Lag-Lead filter 12•Delay Locked Loop 13•Clock recovery circuits 14•Frequency synthesizer
Application Area: 11.Internal clock generation in LSI locked to external clock 22.Frequency Synthesizer for communication systems 33.Clock recovery for communication systems and data storage systems 44.FM demodulation Frequency Synthesizer
Clock Recovery
PLL is a feedback system to match the input signal phase and the output signal phase. Through this process, frequencies of these signals become equal completely.
WAVEFORM IN PLL SYSTEM
Analog phase detector (mixer type)
3 state Phase Frequency Detector This 3 state phase detector is currently most widely used. Because it has a ability for frequency detect.
Dead Zone in PFD The most serious issue of PFD is dead zone at a small phase deviation. This causes a large jitter and a phase noise.
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