SNAS849B December   2024  – September 2026 LMX2624-SP

PRODUCTION DATA  

  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
    8. 5.8 Typical Characteristics
  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
        2. 6.3.7.2 Determining the VCO Gain
        3. 6.3.7.3 Double Buffering (Shadow Registers)
        4. 6.3.7.4 Watchdog Feature
        5. 6.3.7.5 RECAL Feature
      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 Phase Synchronization
        1. 6.3.13.1 General Concept
        2. 6.3.13.2 Categories of Applications for SYNC
        3. 6.3.13.3 Procedure for Using SYNC
      14. 6.3.14 SYSREF
        1. 6.3.14.1 Programmable Fields
        2. 6.3.14.2 Examples
        3. 6.3.14.3 SYSREF Procedure
      15. 6.3.15 Pin-Mode Integer Frequency Generation
        1. 6.3.15.1 4-level Pins Using GPIOs
        2. 6.3.15.2 Pin-Mode Example
      16. 6.3.16 Device Functional Modes
    4. 6.4 Treatment of Unused Pins
    5. 6.5 Programming
      1. 6.5.1 Recommended Initial Power-Up Sequence
      2. 6.5.2 Recommended Sequence for Changing Frequencies
      3. 6.5.3 Register Maps
        1. 6.5.3.1 Device Registers
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 OSCin Configuration
      2. 7.1.2 OSCin Slew Rate
      3. 7.1.3 RF Output Buffer Power Control
      4. 7.1.4 RF Output Buffer
      5. 7.1.5 RF Output Treatment for the Complimentary Side
        1. 7.1.5.1 Single-ended Termination of Unused Output
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curve
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
      3. 7.4.3 Footprint Example on PCB Layout
      4. 7.4.4 Radiation Environments
        1. 7.4.4.1 Total Ionizing Dose
        2. 7.4.4.2 Single Event Effect
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

6.3.7.3 Double Buffering (Shadow Registers)

Double buffering—also known as "shadow registers"—allows the user to program multiple registers without having them actually take effect. When the R0 register is programmed, then these registers take effect. This is especially useful if one wants to change frequencies quickly and multiple register writes are required. When DBL_BUF_EN = 1, the double buffering is enabled for the registers related to VCO, Doubler, PLL, Output MUX and Channel Divider. More details on the registers are available in Register map section.