SNAS834 November   2024 LMK5C22212A

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 Diagrams
    7. 5.7 Typical Characteristics
  7. 6 Parameter Measurement Information
    1. 6.1 Differential Voltage Measurement Terminology
    2. 6.2 Output Clock Test Configurations
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
      1. 7.2.1 PLL Architecture Overview
      2. 7.2.2 DPLL
        1. 7.2.2.1 Independent DPLL Operation
        2. 7.2.2.2 Cascaded DPLL Operation
        3. 7.2.2.3 APLL Cascaded With DPLL
      3. 7.2.3 APLL-Only Mode
    3. 7.3 Feature Description
      1. 7.3.1  Oscillator Input (XO)
      2. 7.3.2  Reference Inputs
      3. 7.3.3  Clock Input Interfacing and Termination
      4. 7.3.4  Reference Input Mux Selection
        1. 7.3.4.1 Automatic Input Selection
        2. 7.3.4.2 Manual Input Selection
      5. 7.3.5  Hitless Switching
        1. 7.3.5.1 Hitless Switching With Phase Cancellation
        2. 7.3.5.2 Hitless Switching With Phase Slew Control
      6. 7.3.6  Gapped Clock Support on Reference Inputs
      7. 7.3.7  Input Clock and PLL Monitoring, Status, and Interrupts
        1. 7.3.7.1 XO Input Monitoring
        2. 7.3.7.2 Reference Input Monitoring
          1. 7.3.7.2.1 Reference Validation Timer
          2. 7.3.7.2.2 Frequency Monitoring
          3. 7.3.7.2.3 Missing Pulse Monitor (Late Detect)
          4. 7.3.7.2.4 Runt Pulse Monitor (Early Detect)
          5. 7.3.7.2.5 Phase Valid Monitor for 1-PPS Inputs
        3. 7.3.7.3 PLL Lock Detectors
        4. 7.3.7.4 Tuning Word History
        5. 7.3.7.5 Status Outputs
        6. 7.3.7.6 Interrupt
      8. 7.3.8  PLL Relationships
        1. 7.3.8.1  PLL Frequency Relationships
          1. 7.3.8.1.1 APLL Phase Frequency Detector (PFD) and Charge Pump
          2. 7.3.8.1.2 APLL VCO Frequency
          3. 7.3.8.1.3 DPLL TDC Frequency
          4. 7.3.8.1.4 DPLL VCO Frequency
          5. 7.3.8.1.5 Clock Output Frequency
        2. 7.3.8.2  Analog PLLs (APLL1, APLL2)
        3. 7.3.8.3  APLL Reference Paths
          1. 7.3.8.3.1 APLL XO Doubler
          2. 7.3.8.3.2 APLL XO Reference (R) Divider
        4. 7.3.8.4  APLL Feedback Divider Paths
          1. 7.3.8.4.1 APLL N Divider With Sigma-Delta Modulator (SDM)
        5. 7.3.8.5  APLL Loop Filters (LF1, LF2)
        6. 7.3.8.6  APLL Voltage-Controlled Oscillators (VCO1, VCO2)
          1. 7.3.8.6.1 VCO Calibration
        7. 7.3.8.7  APLL VCO Clock Distribution Paths
        8. 7.3.8.8  DPLL Reference (R) Divider Paths
        9. 7.3.8.9  DPLL Time-to-Digital Converter (TDC)
        10. 7.3.8.10 DPLL Loop Filter (DLF)
        11. 7.3.8.11 DPLL Feedback (FB) Divider Path
      9. 7.3.9  Output Clock Distribution
      10. 7.3.10 Output Source Muxes
      11. 7.3.11 Output Channel Muxes
      12. 7.3.12 Output Dividers (OD)
      13. 7.3.13 Output Delay
      14. 7.3.14 Clock Outputs
        1. 7.3.14.1 Differential Output
        2. 7.3.14.2 LVCMOS Output
        3. 7.3.14.3 SYSREF/1PPS Output
      15. 7.3.15 Output Auto-Mute During LOL
      16. 7.3.16 Glitchless Output Clock Start-Up
      17. 7.3.17 Clock Output Interfacing and Termination
      18. 7.3.18 Output Synchronization (SYNC)
      19. 7.3.19 Zero-Delay Mode (ZDM)
      20. 7.3.20 DPLL Programmable Phase Delay
      21. 7.3.21 Time Elapsed Counter (TEC)
        1. 7.3.21.1 Configuring TEC Functionality
        2. 7.3.21.2 SPI as a Trigger Source
        3. 7.3.21.3 GPIO Pin as a TEC Trigger Source
          1. 7.3.21.3.1 An Example: Making a Time Elapsed Measurement Using TEC and GPIO1 as Trigger
        4. 7.3.21.4 Other TEC Behavior
    4. 7.4 Device Functional Modes
      1. 7.4.1 DPLL Operating States
        1. 7.4.1.1 Free-Run
        2. 7.4.1.2 Lock Acquisition
        3. 7.4.1.3 DPLL Locked
        4. 7.4.1.4 Holdover
      2. 7.4.2 Digitally-Controlled Oscillator (DCO) Frequency and Phase Adjustment
        1. 7.4.2.1 DPLL DCO Control
        2. 7.4.2.2 DPLL DCO Relative Adjustment Frequency Step Size
        3. 7.4.2.3 APLL DCO Frequency Step Size
      3. 7.4.3 APLL Frequency Control
      4. 7.4.4 Device Start-Up
        1. 7.4.4.1 Device Power-On Reset (POR)
        2. 7.4.4.2 PLL Start-Up Sequence
        3. 7.4.4.3 Start-Up Options for Register Configuration
        4. 7.4.4.4 GPIO1 and SCS_ADD Functionalities
        5. 7.4.4.5 ROM Page Selection
        6. 7.4.4.6 EEPROM Overlay
      5. 7.4.5 Programming
        1. 7.4.5.1 Memory Overview
        2. 7.4.5.2 Interface and Control
          1. 7.4.5.2.1 Programming Through TICS Pro
          2. 7.4.5.2.2 SPI Serial Interface
          3. 7.4.5.2.3 I2C Serial Interface
        3. 7.4.5.3 General Register Programming Sequence
        4. 7.4.5.4 Steps to Program the EEPROM
          1. 7.4.5.4.1 Overview of the SRAM Programming Methods
          2. 7.4.5.4.2 EEPROM Programming With the Register Commit Method
          3. 7.4.5.4.3 EEPROM Programming With the Direct Writes Method or Mixed Method
          4. 7.4.5.4.4 Five MSBs of the I2C Address and the EEPROM Revision Number
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Device Start-Up Sequence
      2. 8.1.2 Power Down (PD#) Pin
      3. 8.1.3 Strap Pins for Start-Up
      4. 8.1.4 Pin States
      5. 8.1.5 ROM and EEPROM
      6. 8.1.6 Power Rail Sequencing, Power Supply Ramp Rate, and Mixing Supply Domains
        1. 8.1.6.1 Power-On Reset (POR) Circuit
        2. 8.1.6.2 Power Up From a Single-Supply Rail
        3. 8.1.6.3 Power Up From Split-Supply Rails
        4. 8.1.6.4 Non-Monotonic or Slow Power-Up Supply Ramp
      7. 8.1.7 Slow or Delayed XO Start-Up
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
      1. 8.4.1 Power Supply Bypassing
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
      3. 8.5.3 Thermal Reliability
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Glossary
    6. 9.6 Electrostatic Discharge Caution
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.7.4 Tuning Word History

The DPLL domain has a tuning word history monitor block that determines the initial output frequency accuracy upon entry into holdover. When in holdover, the stability of the reference clock (on XO input) determines the long-term stability and accuracy of the output frequency. The tuning word can be updated from one of three sources depending on the DPLL operating mode:

  1. Locked Mode: from the output of the digital loop filter when locked
  2. Holdover Mode: from the final output of the history monitor
  3. Free Run Mode: from the free-run tuning word register (user defined)

When the history monitor is enabled and the DPLL is locked, the device averages the reference input frequency by accumulating history from the digital loop filter output during a programmable averaging time (TAVG) set by DPLLx_HIST_TIMER. When a valid reference input becomes invalid, the final tuning word value is stored to determine the initial holdover frequency accuracy. Generally, a longer TAVG time produces a more accurate initial holdover frequency.

If the input reference clock fails and becomes invalid, the history data can be corrupted if the tuning word continues to update before the fail state is indicated by one of the reference input validation monitors. To avoid this scenario, any in progress accumulation is ignored and the recent history data is ignored. The most recent collected average data is discarded such that the actual history used is greater than TAVG but less than 2 × TAVG.

The tuning word history is initially cleared after a device hard reset or soft reset. After the DPLL locks to a new reference, the history monitor waits for the first TAVG timer to expire before storing the first tuning word value and begins to accumulate history. The history monitor does not clear the previous history value during reference switchover or holdover exit. The history can be manually cleared or reset by toggling the history enable bit (DPLLx_HIST_EN = 1 → 0 → 1), if needed.

LMK5C22212A Tuning Word History WindowsFigure 7-21 Tuning Word History Windows

When no tuning word history exists, the free-run tuning word value (DPLLx_FREE_RUN) is used and determines the initial holdover output frequency accuracy.