Fractional/Integer-N PLL Basics (TI)

tingwu7 · 发表于 2011-12-16 13:28:02

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Fractional/Integer-N PLL Basics (TI)

Edited by Curtis Barrett Wireless Communication Business Unit

Contents
Introduction to Phase Locked Loop (PLL) ....................................4
  Frequency Synthesis ..............................................................5
  Digital PLL Synthesis ..............................................................5
PLL Components ......................................................................8
  Voltage Controlled Oscillators (VCO)..........................................8
  Phase Frequency Detectors (PFD)............................................11
  Dividers ................................................................................13
  Loop Filter.............................................................................14
The Simple Math of PLL.............................................................14
  Feedback Loop Analysis..........................................................15
  Loop Transfer Function...........................................................17
Loop Filter Design....................................................................17
  Natural Frequency and Loop Bandwidth....................................18
  Passive Loops and Charge Pump..............................................21
  Lock-up Time and Speed Up ...................................................23
  Loop Order and Type..............................................................24
  Loop Stability and Phase Margin ..............................................24
  Active and Passive Loops Summary..........................................25
  Modulation ............................................................................26
Integer-N PLL...........................................................................27
  Concept ................................................................................27
  Basic Operation ......................................................................29
  Functional Description .............................................................29
  Advantages and Limitations......................................................31
Fractional-N PLL .......................................................................31
  Concept ................................................................................31
  Functional Description ............................................................32
  Divider Dynamics ...................................................................32
  Fractional Accumulator ...........................................................33
  Fractional Spurious Signals and Compensation ..........................34
  Advantages and Limitation.......................................................39
  Comparison...........................................................................39
Phase Noise..............................................................................40
  Definitions and Conversions .....................................................41
  Division and Multiplication Effect................................................43
  Phase Noise Measurements......................................................43
  The Noise Distribution Function L(fm).......................................44
  Noise Sources in PLL ..............................................................44
Spurious Suppression................................................................46
  Reference Spurious Signals .....................................................46
  Fractional Spurious Signals ......................................................47
  Spurious Signal Suppression....................................................47
  The Effect of Phase Noise on System Performance......................47
Loop Response Simulation ........................................................48
  Multi-Loop Design ..................................................................48
Measurements Techniques.........................................................49
  Phase Noise...........................................................................49
  Spurious Signals ....................................................................50
  Switching Speed ....................................................................50
The TI Family of PLL ASICs........................................................51
Summary and FAQ ..................................................................52
Glossary..................................................................................53
References and Further Reading.................................................54