SNAS724A February   2018  – April 2018 LMK05028

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Block Diagram
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
    2. 6.1 Device Start-Up Modes
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Diagrams
    7. 7.7 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Output Clock Test Configurations
  9. 9 Detailed Description
    1. 9.1 Overview
      1. 9.1.1 ITU-T G.8262 (SyncE) Standards Compliance
    2. 9.2 Functional Block Diagrams
      1. 9.2.1 PLL Architecture Overview
      2. 9.2.2 3-Loop Mode
        1. 9.2.2.1 PLL Output Clock Phase Noise Analysis in 3-Loop Mode
      3. 9.2.3 2-Loop REF-DPLL Mode
      4. 9.2.4 2-Loop TCXO-DPLL Mode
      5. 9.2.5 PLL Configurations for Common Applications
    3. 9.3 Feature Description
      1. 9.3.1  Oscillator Input (XO_P/N)
      2. 9.3.2  TCXO/OCXO Input (TCXO_IN)
      3. 9.3.3  Reference Inputs (INx_P/N)
      4. 9.3.4  Clock Input Interfacing and Termination
      5. 9.3.5  Reference Input Mux Selection
        1. 9.3.5.1 Automatic Input Selection
        2. 9.3.5.2 Manual Input Selection
      6. 9.3.6  Hitless Switching
      7. 9.3.7  Gapped Clock Support on Reference Inputs
      8. 9.3.8  Input Clock and PLL Monitoring, Status, and Interrupts
        1. 9.3.8.1 XO Input Monitoring
        2. 9.3.8.2 TCXO Input Monitoring
        3. 9.3.8.3 Reference Input Monitoring
          1. 9.3.8.3.1 Reference Validation Timer
          2. 9.3.8.3.2 Amplitude Monitor
          3. 9.3.8.3.3 Missing Pulse Monitor (Late Detect)
          4. 9.3.8.3.4 Runt Pulse Monitor (Early Detect)
          5. 9.3.8.3.5 Frequency Monitoring
          6. 9.3.8.3.6 Phase Valid Monitor for 1-PPS Inputs
        4. 9.3.8.4 PLL Lock Detectors
        5. 9.3.8.5 Tuning Word History
        6. 9.3.8.6 Status Outputs
        7. 9.3.8.7 Interrupt
      9. 9.3.9  PLL Channels
        1. 9.3.9.1  PLL Frequency Relationships
        2. 9.3.9.2  Analog PLL (APLL)
        3. 9.3.9.3  APLL XO Doubler
        4. 9.3.9.4  APLL Phase Frequency Detector (PFD) and Charge Pump
        5. 9.3.9.5  APLL Loop Filter
        6. 9.3.9.6  APLL Voltage Controlled Oscillator (VCO)
          1. 9.3.9.6.1 VCO Calibration
        7. 9.3.9.7  APLL VCO Post-Dividers (P1, P2)
        8. 9.3.9.8  APLL Fractional N Divider (N) With SDM
        9. 9.3.9.9  REF-DPLL Reference Divider (R)
        10. 9.3.9.10 TCXO/OCXO Input Doubler and M Divider
        11. 9.3.9.11 TCXO Mux
        12. 9.3.9.12 REF-DPLL and TCXO-DPLL Time-to-Digital Converter (TDC)
        13. 9.3.9.13 REF-DPLL and TCXO-DPLL Loop Filter
        14. 9.3.9.14 REF-DPLL and TCXO-DPLL Feedback Dividers
      10. 9.3.10 Output Clock Distribution
      11. 9.3.11 Output Channel Muxes
        1. 9.3.11.1 TCXO/Ref Bypass Mux
      12. 9.3.12 Output Dividers
      13. 9.3.13 Clock Outputs (OUTx_P/N)
        1. 9.3.13.1 AC-Differential Output (AC-DIFF)
        2. 9.3.13.2 HCSL Output
        3. 9.3.13.3 LVCMOS Output (1.8 V, 2.5 V)
        4. 9.3.13.4 Output Auto-Mute During LOL or LOS
      14. 9.3.14 Glitchless Output Clock Start-Up
      15. 9.3.15 Clock Output Interfacing and Termination
      16. 9.3.16 Output Synchronization (SYNC)
      17. 9.3.17 Zero-Delay Mode (ZDM) Configuration
      18. 9.3.18 PLL Cascading With Internal VCO Loopback
    4. 9.4 Device Functional Modes
      1. 9.4.1 Device Start-Up Modes
        1. 9.4.1.1 EEPROM Mode
        2. 9.4.1.2 ROM Mode
      2. 9.4.2 PLL Operating Modes
        1. 9.4.2.1 Free-Run Mode
        2. 9.4.2.2 Lock Acquisition
        3. 9.4.2.3 Locked Mode
        4. 9.4.2.4 Holdover Mode
      3. 9.4.3 PLL Start-Up Sequence
      4. 9.4.4 Digitally-Controlled Oscillator (DCO) Mode
        1. 9.4.4.1 DCO Frequency Step Size
        2. 9.4.4.2 DCO Direct-Write Mode
      5. 9.4.5 Zero-Delay Mode (ZDM)
      6. 9.4.6 Cascaded PLL Operation
    5. 9.5 Programming
      1. 9.5.1 Interface and Control
      2. 9.5.2 I2C Serial Interface
        1. 9.5.2.1 I2C Block Register Transfers
      3. 9.5.3 SPI Serial Interface
        1. 9.5.3.1 SPI Block Register Transfer
      4. 9.5.4 Register Map Generation
      5. 9.5.5 General Register Programming Sequence
      6. 9.5.6 EEPROM Programming Flow
        1. 9.5.6.1 EEPROM Programming Using Register Commit (Method #1)
          1. 9.5.6.1.1 Write SRAM Using Register Commit
          2. 9.5.6.1.2 Program EEPROM
        2. 9.5.6.2 EEPROM Programming Using Direct SRAM Writes (Method #2)
          1. 9.5.6.2.1 Write SRAM Using Direct Writes
      7. 9.5.7 Read SRAM
      8. 9.5.8 Read EEPROM
      9. 9.5.9 EEPROM Start-Up Mode Default Configuration
    6. 9.6 Register Maps
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Device Start-Up Sequence
      2. 10.1.2 Power Down (PDN) Pin
      3. 10.1.3 Power Rail Sequencing, Power Supply Ramp Rate, and Mixing Supply Domains
        1. 10.1.3.1 Mixing Supplies
        2. 10.1.3.2 Power-On Reset (POR) Circuit
        3. 10.1.3.3 Powering Up From a Single-Supply Rail
        4. 10.1.3.4 Power Up From Split-Supply Rails
        5. 10.1.3.5 Non-Monotonic or Slow Power-Up Supply Ramp
      4. 10.1.4 Slow or Delayed XO Start-Up
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curves
    3. 10.3 Do's and Don'ts
  11. 11Power Supply Recommendations
    1. 11.1 Power Supply Bypassing
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Thermal Reliability
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Clock Architect
      2. 13.1.2 TICS Pro
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

9.3.2 TCXO/OCXO Input (TCXO_IN)

The TCXO input is the reference clock to the TCXO-DPLL loop in each PLL channel. When the PLL channel uses the TCXO-DPLL, the TCXO input source determines the close-in phase noise and wander performance (MTIE/TDEV) when the DPLL is locked, as well as the frequency accuracy and stability in free-run and holdover modes. A TCXO input with high phase noise floor should have minimal or no impact on the output jitter performance, provided the TCXO loop bandwidth is designed low enough to attenuate its noise contribution. This input can be driven from a low-frequency TCXO, OCXO, or external traceable clock that conforms to the frequency accuracy and holdover stability requirements of the application. TCXO and OCXO frequencies of 10 to 12.8 MHz are widely available and cost-effective options.

The TCXO input can accept an AC-coupled single-ended clock (sine, clipped-sine, or square wave) and has an internal weak bias of about 0.6 V. The input voltage swing should be less than 1.3 Vpp and terminated before AC-coupling to the pin. If unused, the TCXO input buffer can be powered down by register bit and the pin can be left floating.

The buffered TCXO path also drives the input monitoring blocks as well as the TCXO/Ref bypass mux to the output muxes, allowing a buffered copy of the TCXO input on OUT0 and/or OUT1.

LMK05028 lmk05028-tcxo-sch.gifFigure 25. TCXO Input Buffer