SNAS855F November   2023  – November 2025 LMKDB1102 , LMKDB1104 , LMKDB1108 , LMKDB1120

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information 
    5. 6.5 Electrical Characteristics
    6. 6.6 SMBus Timing Requirements
    7. 6.7 SBI Timing Requirements
    8. 6.8 Timing Diagrams
    9. 6.9 Typical Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Input Features
        1. 8.3.1.1 Running Input Clocks When Device is Powered Off
        2. 8.3.1.2 Fail-Safe Inputs
        3. 8.3.1.3 Input Configurations
          1. 8.3.1.3.1 Internal Termination for Clock Inputs
          2. 8.3.1.3.2 AC-Coupled or DC-Coupled Clock Inputs
      2. 8.3.2 Flexible Power Sequence
        1. 8.3.2.1 PWRDN# Assertion and Deassertion
        2. 8.3.2.2 OE# Assertion and Deassertion
        3. 8.3.2.3 Clock Input and PWRGD/PWRDN# Behaviors When Device Power is Off
      3. 8.3.3 LOS and OE
        1. 8.3.3.1 Additional OE# Pins for LMKDB1120 and Backward Compatibility
        2. 8.3.3.2 Synchronous OE
        3. 8.3.3.3 OE Control
        4. 8.3.3.4 Automatic Output Disable
        5. 8.3.3.5 LOS Detection
      4. 8.3.4 Output Features
        1. 8.3.4.1 Double Termination
        2. 8.3.4.2 Programmable Output Slew Rate
          1. 8.3.4.2.1 Slew Rate Control through Pin
          2. 8.3.4.2.2 Slew Rate Control Through SMBus
        3. 8.3.4.3 Programmable Output Swing
        4. 8.3.4.4 Accurate Output Impedance
        5. 8.3.4.5 Programmable Output Impedance
        6. 8.3.4.6 Fail-Safe Outputs
    4. 8.4 Device Functional Modes
      1. 8.4.1 SMBus Mode
      2. 8.4.2 SBI Mode
      3. 8.4.3 Pin Mode
  10. 9 Register Maps
    1. 9.1 LMKDB1120 and LMKDB1120FS Registers
    2. 9.2 LMKDB1112 Registers
    3. 9.3 LMKDB1108 and LMKDB1108FS Registers
    4. 9.4 LMKDB1104 and LMKDB1104FS Registers
  11. 10Application and Implementation
    1. 10.1 Application Information
    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 Power Supply Recommendations
    4. 10.4 Layout
      1. 10.4.1 Layout Guidelines
      2. 10.4.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information
    1. 13.1 Mechanical Data

Package Options

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

10.2.1 Design Requirements

Find two buffers for PCIe clock fan-out and Ethernet clock fan-out separately. Jitter requirements must be met and space must be minimized.

Table 10-1 Design Parameters
PARAMETER VALUE
Number of PCIe clocks 15
Number of 156.25MHz Ethernet clocks 7
PCIe architecture CC (Common Clock)
PCIe reference clock slew rate ≥3.5V/ns
PCIe Gen 5 reference clock jitter 45fs maximum
PCIe Gen 5 total jitter 50fs maximum
156.25MHz reference clock slew rate ≥3.5V/ns
156.25MHz reference clock jitter (12kHz to 20MHz) 90fs maximum
156.25MHz total jitter (12kHz to 20MHz) 100fs maximum