SI5340D-D-GM vs LTC6948IUFD-1#TRPBF
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| Category | Clock/Timing - Clock Generators, PLLs, Frequency Synthesizers | Clock/Timing - Clock Generators, PLLs, Frequency Synthesizers |
| Manufacturer | Skyworks Solutions Inc. | Analog Devices Inc. |
| Description | IC JITTER ATTENUATOR/MULTIPLEXER | IC FRACTIONAL-N PLL W/VCO 28QFN |
| Package | Tape & Reel (TR) | Cut Tape (CT) |
| Series | - | - |
| Type | - | Clock/Frequency Synthesizer (RF/IF), Fractional N |
| Voltage - Supply | 1.71V ~ 3.47V | 3.15V ~ 5.25V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 105°C |
| Mounting Type | Surface Mount | Surface Mount |
| Package / Case | 44-VFQFN Exposed Pad | 28-WFQFN Exposed Pad |
| Supplier Device Package | 44-QFN (7x7) | 28-QFN (4x5) |
| Output | CML, HCSL, LVCMOS, LVDS, LVPECL | Clock |
| Frequency - Max | 350MHz | 3.74GHz |
| Number of Circuits | 1 | 1 |
| Input | LVCMOS, LVDS, LVPECL, Crystal | Clock |
| PLL | Yes | Yes |
| Ratio - Input:Output | 4:4 | 1:1 |
| 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. What is a PLL clock generator?
A PLL clock generator (Phase-Locked Loop Clock Generator) is an electronic circuit used to generate and adjust a clock signal. It automatically adjusts the frequency of the internal oscillator by comparing the phase difference between the input signal and the output signal of the internal oscillator so that the phase of the output signal is synchronized with the input signal. PLL clock generator is mainly used to generate high-speed and stable clock signal to provide timing reference for communication system.
The key components of PLL clock generator include:
Phase detector: compare the phase difference between input signal and feedback signal.
Charge pump: adjust the voltage to control the frequency of VCO according to the output of phase detector.
Loop filter: smooth the output of charge pump and reduce noise.
Voltage controlled oscillator (VCO): change the oscillation frequency according to the control voltage to generate output clock signal.
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3. What are frequency synthesizers used for?
The main purpose of frequency synthesizers is to provide specific frequency signals for radio and communication systems. It is an important component of modern electronic systems and is widely used in communication, radar, navigation and other equipment.
Frequency synthesizers generate a large number of discrete frequencies with the same stability and accuracy from one or more reference signal sources with high frequency stability and accuracy through linear operations in the frequency domain. Specifically, frequency synthesizers use techniques such as frequency multiplication, frequency division, and mixing to obtain discrete frequency signals with the same stability as the reference signal. -
4. What are the three types of frequency synthesizers?
There are three main types of frequency synthesizers: direct analog frequency synthesis, indirect frequency synthesis, and direct digital frequency synthesis.
Direct analog frequency synthesis: This method uses one or more different crystal oscillators as reference signal sources to directly generate many discrete frequency output signals through frequency multiplication, frequency division, mixing, etc. The advantages of direct analog frequency synthesis are high long-term and short-term frequency stability and fast frequency conversion speed, but it is difficult to debug and difficult to suppress spurious signals.
Indirect frequency synthesis: also known as phase-locked loop frequency synthesis technology (PLL), using one or several reference frequency sources, through harmonic generator mixing and frequency division, etc. to generate a large number of harmonics or combined frequencies, and then use a phase-locked loop to lock the frequency of the voltage-controlled oscillator to a certain harmonic or combined frequency. The advantages of indirect frequency synthesis are low cost and the ability to synthesize any frequency, but slow response, mainly used in civilian equipment.
Direct digital frequency synthesis: This method performs frequency synthesis based on the concept of phase, using digital sampling and storage technology, with the advantages of precise phase and frequency resolution, fast conversion time, etc. The key components of direct digital frequency synthesis include digital-to-analog converters, phase accumulators, and memories, etc., which store the required waveform version in digital format and create signals.
