SNAS881B April   2025  – October 2025 LMK3C0105-Q1

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 I2C Interface Specification
  7. 6 Parameter Measurement Information
    1. 6.1 Output Format Configurations
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device Block-Level Description
      2. 7.3.2 Device Configuration Control
      3. 7.3.3 OTP Mode
      4. 7.3.4 I2C Mode
    4. 7.4 Device Functional Modes
      1. 7.4.1 Fail-Safe Inputs
      2. 7.4.2 Fractional Output Dividers
        1. 7.4.2.1 FOD Operation
        2. 7.4.2.2 Digital State Machine
        3. 7.4.2.3 Spread-Spectrum Clocking
        4. 7.4.2.4 Integer Boundary Spurs
      3. 7.4.3 Output Behavior
        1. 7.4.3.1 Output Format Selection
        2. 7.4.3.2 REF_CTRL Operation
      4. 7.4.4 Output Enable
        1. 7.4.4.1 Output Enable Control
        2. 7.4.4.2 Output Enable Polarity
        3. 7.4.4.3 Separate Output Enable
        4. 7.4.4.4 Output Disable Behavior
      5. 7.4.5 Device Default Settings
    5. 7.5 Programming
      1. 7.5.1 I2C Serial Interface
      2. 7.5.2 One-Time Programming Sequence
  9. 8 Device Registers
    1. 8.1 Register Maps
      1. 8.1.1  R0 Register (Address = 0x0) [reset = 0x0861/0x0863]
      2. 8.1.2  R1 Register (Address = 0x1) [reset = 0x5599]
      3. 8.1.3  R2 Register (Address = 0x2) [reset = 0xC28F]
      4. 8.1.4  R3 Register (Address = 0x3) [reset = 0x1804]
      5. 8.1.5  R4 Register (Address = 0x4) [reset = 0x0000]
      6. 8.1.6  R5 Register (Address = 0x5) [reset = 0x0000]
      7. 8.1.7  R6 Register (Address = 0x6) [reset = 0x0AA7]
      8. 8.1.8  R7 Register (Address = 0x7) [reset = 0x5D1F]
      9. 8.1.9  R8 Register (Address = 0x8) [reset = 0xC28F]
      10. 8.1.10 R9 Register (Address = 0x9) [reset = 0x3000/0x1000]
      11. 8.1.11 R10 Register (Address = 0xA) [reset = 0x0010]
      12. 8.1.12 R11 Register (Address = 0xB) [reset = 0x4000]
      13. 8.1.13 R12 Register (Address = 0xC) [reset = 0x6800]
      14. 8.1.14 R238 Register (Address = 0xEE) [reset = 0x0000]
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Application Block Diagram Examples
      2. 9.2.2 Design Requirements
      3. 9.2.3 Detailed Design Procedure
        1. 9.2.3.1 Example: Changing Output Frequency
        2. 9.2.3.2 Crosstalk
        3. 9.2.3.3 Application Curves
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 Power-Up Sequencing
      2. 9.3.2 Decoupling Power Supply Inputs
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

9.2.2 Design Requirements

Consider a typical Gigabit Ethernet Switch application. In a system such as this, the clocks are expected to be available upon request without the need for any additional device-level programming. The default device configuration outputs five 25MHz LVCMOS clocks, all enabled by default. A typical output clock requirement in this application is two 25MHz LVCMOS clocks for the PHY, and both a 25MHz and 100MHz LVCMOS clock for the FPGA. The section below describes the detailed design procedure to generate the required output frequencies for the above scenario using the LMK3C0105-Q1.