SNAS849 December   2024 LMX2624-SP

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements
    7. 5.7 Timing Diagrams
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Reference Oscillator Input
      2. 6.3.2  Reference Path
        1. 6.3.2.1 OSCin Doubler (OSC_2X)
        2. 6.3.2.2 Pre-R Divider (PLL_R_PRE)
        3. 6.3.2.3 Post-R Divider (PLL_R)
      3. 6.3.3  State Machine Clock
      4. 6.3.4  PLL Phase Detector and Charge Pump
      5. 6.3.5  N Divider and Fractional Circuitry
      6. 6.3.6  MUXout Pin
        1. 6.3.6.1 Serial Data Output for Readback
        2. 6.3.6.2 Lock Detect Indicator Set as Type “VCOcal” or "Vtune and VCOcal"
      7. 6.3.7  VCO (Voltage-Controlled Oscillator)
        1. 6.3.7.1 VCO Calibration
          1. 6.3.7.1.1 Double Buffering (Shadow Registers)
        2. 6.3.7.2 Watchdog Feature
        3. 6.3.7.3 RECAL Feature
        4. 6.3.7.4 Determining the VCO Gain
      8. 6.3.8  Channel Divider
      9. 6.3.9  Output Mute Pin and Ping Pong Approaches
      10. 6.3.10 Output Frequency Doubler
      11. 6.3.11 Output Buffer
      12. 6.3.12 Power-Down Modes
      13. 6.3.13 Pin-Mode Integer Frequency Generation
      14. 6.3.14 Treatment of Unused Pins
      15. 6.3.15 Phase Synchronization
        1. 6.3.15.1 General Concept
        2. 6.3.15.2 Categories of Applications for SYNC
        3. 6.3.15.3 Procedure for Using SYNC
        4. 6.3.15.4 SYNC Input Pin
      16. 6.3.16 Phase Adjust
      17. 6.3.17 Fine Adjustments for Phase Adjust and Phase SYNC
      18. 6.3.18 SYSREF
        1. 6.3.18.1 Programmable Fields
        2. 6.3.18.2 Input and Output Pin Formats
          1. 6.3.18.2.1 SYSREF Output Format
        3. 6.3.18.3 Examples
        4. 6.3.18.4 SYSREF Procedure
    4. 6.4 Device Functional Modes
    5. 6.5 Programming
      1. 6.5.1 Recommended Initial Power-Up Sequence
      2. 6.5.2 Recommended Sequence for Changing Frequencies
  8. 7 Register Maps
    1. 7.1 Device Registers
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 OSCin Configuration
      2. 8.1.2 OSCin Slew Rate
      3. 8.1.3 RF Output Buffer Power Control
      4. 8.1.4 RF Output Buffer Pullup
      5. 8.1.5 RF Output Treatment for the Complimentary Side
        1. 8.1.5.1 Single-ended Termination of Unused Output
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
      3. 8.4.3 Footprint Example on PCB Layout
      4. 8.4.4 Radiation Environments
        1. 8.4.4.1 Total Ionizing Dose
        2. 8.4.4.2 Single Event Effect
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Engineering Samples
    2. 11.2 Package Option Addendum
    3. 11.3 Tape and Reel Information

8.2.1 Design Requirements

The design of the loop filter is complex and is typically done with software. The PLLatinum Sim software is an excellent resource for doing this and the design is shown in Figure 8-4. For those interested in the equations involved, the PLL Performance, Simulation, and Design Handbook (SNAA106) goes into great detail as to theory and design of PLL loop filters.

LMX2624-SP PLLatinum Sim Tool Figure 8-4 PLLatinum Sim Tool