LMK04010BISQE/NOPB vs 8T49N222B-108NLGI
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| Category | Clock/Timing - Clock Generators, PLLs, Frequency Synthesizers | Clock/Timing - Clock Generators, PLLs, Frequency Synthesizers |
| Manufacturer | National Semiconductor | Renesas Electronics America Inc |
| Description | LMK04010 LOW-NOISE CLOCK JITTER | IC TRANSLATOR UNIV FREQ 48VFQFN |
| Package | Bulk | Tape & Reel (TR) |
| Series | - | FemtoClock® NG |
| Type | Clock Conditioner | - |
| Voltage - Supply | 3.15V ~ 3.45V | 2.375V ~ 3.465V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
| Package / Case | 48-WFQFN Exposed Pad | 48-VFQFN Exposed Pad |
| Supplier Device Package | 48-WQFN (7x7) | 48-VQFN (7x7) |
| Output | 2VPECL, LVPECL | LVDS |
| Frequency - Max | 1.296GHz | 122.88MHz |
| Number of Circuits | 1 | 1 |
| Input | LVCMOS, LVDS, LVPECL | HCSL, LVDS, LVHSTL, LVPECL, Crystal |
| PLL | Yes | Yes with Bypass |
| Ratio - Input:Output | 2:5 | 3:2 |
| Differential - Input:Output | Yes/Yes | Yes/Yes |
| Divider/Multiplier | Yes/Yes | Yes/No |
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1. How does Phase-locked loops（PLL） work?
PLL (phase locked loop) is a feedback control circuit that continuously adjusts the frequency and phase of the internal oscillation signal to synchronize with the input reference signal by comparing the phase difference between the input signal and the feedback signal. PLL is mainly composed of phase detector (PD), loop filter (LF), voltage controlled oscillator (VCO) and optional divider (Divider).
When PLL starts working, the frequency of input reference signal is always different from the inherent oscillation frequency of voltage controlled oscillator, resulting in constant phase difference. The error voltage output by the phase detector is converted into a control voltage through a loop filter and added to the voltage-controlled oscillator, so that its frequency is gradually adjusted to synchronize with the input reference signal and enter the "locked" state. If the frequency and phase of the input reference signal change, the PLL controls the frequency and phase of the voltage-controlled oscillator to track the changes of the input reference signal and re-enter the locked state. -
2. Why do clocks use PLL?
The reason why clocks use PLL is because PLL can provide a stable high-frequency clock signal to ensure the precise operation and synchronization of electronic systems. PLL (Phase Locked Loop) compares the phase difference between the input signal and the output signal generated by the voltage-controlled oscillator (VCO) and adjusts the frequency of the VCO so that the phase of the output signal is synchronized with the phase of the input signal. This synchronization process is achieved through a closed-loop feedback system, which ensures the stability and accuracy of the clock signal.
The main functions of PLL include:
Providing a stable high-frequency clock signal: PLL generates a stable high-frequency clock based on the reference clock provided by the oscillator to ensure stable circuit timing.
Frequency synthesis: PLL can multiply or divide the frequency of the input signal to generate a clock signal of the required frequency.
Phase control: By adjusting the phase of the output signal, it ensures synchronization with the input signal and reduces phase deviation.
In modern electronic systems, the role of clock signals is very important. It is not only used to synchronize the operation of various components and ensure that key time parameters are within the allowable range, but also regulates the connection speed of data transmission in communication systems. The application of PLL ensures the accuracy and stability of the clock signal and improves the performance and reliability of the entire system. -
3. What is the difference between PLL and oscillator?
The main difference between PLL and oscillator lies in their functions and features. PLL has the ability of phase locking and frequency tracking, which can provide higher frequency stability, especially in the presence of an external reference signal. Oscillators usually generate fixed-frequency signals and do not have these functions of PLL.
Specifically, oscillators are devices used to generate periodic signals. Common types include RC oscillators, LC oscillators, and crystal oscillators. RC oscillators have a simple structure and low cost, but poor frequency stability and accuracy; LC oscillators have good frequency stability, but are large in size and high in cost; crystal oscillators have extremely high frequency stability, but are expensive.
PLL is a feedback control circuit that can compare the output of the oscillator with a reference signal, generate a control voltage based on the phase difference, and thus adjust the frequency and phase of the oscillator to synchronize it with the reference signal. PLL can generate output signals with higher or lower frequencies than the reference signal, and is usually more complex to design and implement than oscillators, with higher power consumption and cost.
Whether to choose an oscillator or PLL depends on the specific application requirements. If a fixed frequency signal is required and cost and complexity are a concern, an oscillator is the appropriate choice. If precise frequency control and low phase noise are required and a stable reference signal is available in the system, a PLL is a better choice. -
4. What are frequency synthesizers used for?
Frequency synthesizers have a wide range of applications in many fields, mainly including the following aspects:
Communication systems: In communication systems, frequency synthesizers are used to generate carrier frequencies and modulation signals to ensure the normal operation of communication equipment and the stability of signal transmission. It can provide high-precision and stable frequency signals to meet the requirements of communication systems for frequency accuracy and stability.
Radar systems: Radar systems require accurate frequency synthesis to ensure functions such as beam pointing and target tracking. Frequency synthesizers play a key role in radar systems, providing precise frequency control to ensure the performance and accuracy of radar systems.
Radio equipment: Radio equipment requires frequency synthesizers to generate signals of different frequencies for modulation and demodulation, signal transmission and reception, etc., to ensure effective communication between devices. The high accuracy and stability of frequency synthesizers enable radio equipment to work efficiently.
Instrumentation and test equipment: Frequency synthesizers are used in test and measurement applications as standard signal sources. It can generate high-precision and stable frequency signals to meet the signal quality requirements of laboratory test and measurement equipment.
Electronic countermeasure equipment: In electronic countermeasures, frequency synthesizers can be used as jammers to interfere with enemy communications and radar systems by generating signals of multiple frequencies. Its high flexibility and rapid response make it important in electronic countermeasures.
Other applications: Frequency synthesizers are also widely used in remote control and telemetry communications, navigation, and radio and television. For example, in shortwave frequency hopping communications, frequency synthesizers can quickly switch frequencies and phases to meet the requirements of fast frequency hopping communications.
