LMK04803BISQX/NOPB vs LMK04808BISQX/NOPB
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| Category | Clock/Timing - Clock Generators, PLLs, Frequency Synthesizers | Clock/Timing - Clock Generators, PLLs, Frequency Synthesizers |
| Manufacturer | Texas Instruments | Texas Instruments |
| Description | IC CLOCK DUAL PLL 64WQFN | IC CLOCK DUAL PLL 64WQFN |
| Package | Tube | Tube |
| Series | PLLatinum™ | PLLatinum™ |
| Type | Jitter Cleaner | Jitter Cleaner |
| Voltage - Supply | 3.15V ~ 3.45V | 3.15V ~ 3.45V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
| Package / Case | 64-WFQFN Exposed Pad | 64-WFQFN Exposed Pad |
| Supplier Device Package | 64-WQFN (9x9) | 64-WQFN (9x9) |
| Output | LVCMOS, LVDS, LVPECL | LVCMOS, LVDS, LVPECL |
| Frequency - Max | 1.536GHz | 1.536GHz |
| Number of Circuits | 1 | 1 |
| Input | LVCMOS, LVDS, LVPECL | LVCMOS, LVDS, LVPECL |
| PLL | Yes | Yes |
| Ratio - Input:Output | 2:14 | 2:14 |
| Differential - Input:Output | Yes/Yes | Yes/Yes |
| Divider/Multiplier | Yes/No | Yes/No |
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1. What is the difference between a PLL and a synthesizer?
The main difference between a PLL (phase-locked loop) and a synthesizer lies in their functions and application scenarios. PLL is mainly used to achieve phase locking of the output signal with the input signal, while a synthesizer is used to generate output signals of multiple frequencies.
PLL (Phase Locked Loop) is a circuit used to lock the phase. It consists of three main parts: a phase detector (PD), a low-pass filter (LPF), and a voltage-controlled crystal oscillator (VCO).
A synthesizer is a device used to generate output signals of multiple frequencies. It realizes the frequency synthesis function by adding a frequency divider on the basis of PLL. Synthesizers can be divided into integer frequency synthesizers and fractional frequency synthesizers. -
2. 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. -
3. How does PLL increase frequency?
PLL (phase-locked loop) is usually used to increase or decrease the frequency of a signal. Increasing the frequency usually involves increasing the value of the feedback divider, while decreasing the frequency involves increasing or adjusting the gain followed by a divider.
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4. 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.
