SNAS844A November   2024  – August 2026 LMK5B12212

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 Timing Diagrams
    7. 6.7 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Differential Voltage Measurement Terminology
    2. 7.2 Output Clock Test Configurations
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
      1. 8.2.1 PLL Architecture Overview
      2. 8.2.2 DPLL
        1. 8.2.2.1 Independent DPLL Operation
        2. 8.2.2.2 APLL Cascaded With DPLL
      3. 8.2.3 APLL-Only Mode
    3. 8.3 Feature Description
      1. 8.3.1  Oscillator Input (XO)
      2. 8.3.2  Reference Inputs
      3. 8.3.3  Clock Input Interfacing and Termination
      4. 8.3.4  Reference Input Mux Selection
        1. 8.3.4.1 Automatic Input Selection
        2. 8.3.4.2 Manual Input Selection
      5. 8.3.5  Hitless Switching
        1. 8.3.5.1 Hitless Switching With Phase Cancellation
        2. 8.3.5.2 Hitless Switching With Phase Slew Control
      6. 8.3.6  Gapped Clock Support on Reference Inputs
      7. 8.3.7  Input Clock and PLL Monitoring, Status, and Interrupts
        1. 8.3.7.1 XO Input Monitoring
        2. 8.3.7.2 Reference Input Monitoring
          1. 8.3.7.2.1 Reference Validation Timer
          2. 8.3.7.2.2 Frequency Monitoring
          3. 8.3.7.2.3 Missing Pulse Monitor (Late Detect)
          4. 8.3.7.2.4 Runt Pulse Monitor (Early Detect)
          5. 8.3.7.2.5 Phase Valid Monitor for 1PPS Inputs
        3. 8.3.7.3 PLL Lock Detectors
        4. 8.3.7.4 Tuning Word History
        5. 8.3.7.5 Status Outputs
        6. 8.3.7.6 Interrupt
      8. 8.3.8  PLL Relationships
        1. 8.3.8.1  PLL Frequency Relationships
          1. 8.3.8.1.1 APLL Phase Frequency Detector (PFD) and Charge Pump
          2. 8.3.8.1.2 APLL VCO Frequency
          3. 8.3.8.1.3 DPLL TDC Frequency
          4. 8.3.8.1.4 DPLL VCO Frequency
          5. 8.3.8.1.5 Clock Output Frequency
        2. 8.3.8.2  Analog PLLs (APLL1, APLL2)
        3. 8.3.8.3  APLL Reference Paths
          1. 8.3.8.3.1 APLL XO Doubler
          2. 8.3.8.3.2 APLL XO Reference (R) Divider
        4. 8.3.8.4  APLL Feedback Divider Paths
          1. 8.3.8.4.1 APLL N Divider With Sigma-Delta Modulator (SDM)
        5. 8.3.8.5  APLL Loop Filters (LF1, LF2)
        6. 8.3.8.6  APLL Voltage-Controlled Oscillators (VCO1, VCO2)
          1. 8.3.8.6.1 VCO Calibration
        7. 8.3.8.7  APLL VCO Clock Distribution Paths
        8. 8.3.8.8  DPLL Reference (R) Divider Paths
        9. 8.3.8.9  DPLL Time-to-Digital Converter (TDC)
        10. 8.3.8.10 DPLL Loop Filter (DLF)
        11. 8.3.8.11 DPLL Feedback (FB) Divider Path
      9. 8.3.9  Output Clock Distribution
      10. 8.3.10 Output Source Muxes
      11. 8.3.11 Output Channel Muxes
      12. 8.3.12 Output Dividers (OD)
      13. 8.3.13 Output Delay
      14. 8.3.14 Clock Output Drivers
        1. 8.3.14.1 Differential Output
        2. 8.3.14.2 LVCMOS Output
        3. 8.3.14.3 SYSREF/1PPS Output
      15. 8.3.15 Output Auto-Mute During LOL
      16. 8.3.16 Glitchless Output Clock Start-Up
      17. 8.3.17 Clock Output Interfacing and Termination
      18. 8.3.18 Output Synchronization (SYNC)
      19. 8.3.19 Zero-Delay Mode (ZDM)
      20. 8.3.20 DPLL Programmable Phase Delay
      21. 8.3.21 Time Elapsed Counter (TEC)
        1. 8.3.21.1 Configuring TEC Functionality
        2. 8.3.21.2 SPI as a Trigger Source
        3. 8.3.21.3 GPIO Pin as a TEC Trigger Source
          1. 8.3.21.3.1 An Example: Making a Time Elapsed Measurement Using TEC and GPIO1 as Trigger
        4. 8.3.21.4 Other TEC Behavior
    4. 8.4 Device Functional Modes
      1. 8.4.1 DPLL Operating States
        1. 8.4.1.1 Free-Run
        2. 8.4.1.2 Lock Acquisition
        3. 8.4.1.3 DPLL Locked
        4. 8.4.1.4 Holdover
      2. 8.4.2 Digitally-Controlled Oscillator (DCO) Frequency and Phase Adjustment
        1. 8.4.2.1 DPLL DCO Control
        2. 8.4.2.2 DPLL DCO Relative Adjustment Frequency Step Size
        3. 8.4.2.3 APLL DCO Frequency Step Size
      3. 8.4.3 APLL Frequency Control
      4. 8.4.4 Device Start-Up
        1. 8.4.4.1 Device Power-On Reset (POR)
        2. 8.4.4.2 PLL Start-Up Sequence
        3. 8.4.4.3 Start-Up Options for Register Configuration
        4. 8.4.4.4 GPIO1 and SCS_ADD Functionalities
        5. 8.4.4.5 ROM Page Selection
        6. 8.4.4.6 ROM Detailed Description
        7. 8.4.4.7 EEPROM Overlay
      5. 8.4.5 Programming
        1. 8.4.5.1 Memory Overview
        2. 8.4.5.2 Interface and Control
          1. 8.4.5.2.1 Programming Through TICS Pro
          2. 8.4.5.2.2 SPI Serial Interface
          3. 8.4.5.2.3 I2C Serial Interface
        3. 8.4.5.3 General Register Programming Sequence
        4. 8.4.5.4 Steps to Program the EEPROM
          1. 8.4.5.4.1 Overview of the SRAM Programming Methods
          2. 8.4.5.4.2 EEPROM Programming With the Register Commit Method
          3. 8.4.5.4.3 EEPROM Programming With the Direct Writes Method or Mixed Method
          4. 8.4.5.4.4 Five MSBs of the I2C Address and the EEPROM Revision Number
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Device Start-Up Sequence
      2. 9.1.2 Power Down (PD#) Pin
      3. 9.1.3 Strap Pins for Start-Up
      4. 9.1.4 Pin States
      5. 9.1.5 ROM and EEPROM
      6. 9.1.6 Power Rail Sequencing, Power Supply Ramp Rate, and Mixing Supply Domains
        1. 9.1.6.1 Power-On Reset (POR) Circuit
        2. 9.1.6.2 Power Up From a Single-Supply Rail
        3. 9.1.6.3 Power Up From Split-Supply Rails
        4. 9.1.6.4 Non-Monotonic or Slow Power-Up Supply Ramp
      7. 9.1.7 Slow or Delayed XO Start-Up
      8. 9.1.8 Powering XO Using APLL2 LDO
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
    3. 9.3 Best Design Practices
    4. 9.4 Power Supply Recommendations
      1. 9.4.1 Power Supply Bypassing
    5. 9.5 Layout
      1. 9.5.1 Layout Guidelines
      2. 9.5.2 Layout Example
      3. 9.5.3 Thermal Reliability
  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 Glossary
    6. 10.6 Electrostatic Discharge Caution
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

9.1.8 Powering XO Using APLL2 LDO

If the XO is being powered by a noisy supply, such as a buck, noise that is generated by the XO appears at the clock output as well if the XO has a poor power supply noise ratio (PSNR). In some cases, CAP1_APLL2 (pin 22) can be used as an alternative supply to the XO to provide a more stable input reference. Figure 9-3 shows a simple block diagram of how the APLL2 LDO can be used to supply an external XO.

For proper functionality in this use case, the design must meet the following requirements:

  • APLL2 must not be in use
  • The current through the LDO must not exceed 20mA
  • For the best PSRR performance, the APLL2 LDO must be enabled with VCO2 powered off
  • To output 2.6V from the CAP1_APLL2 pin, the following APLL2 enable sequence must be used with a minimum 2ms delay between each step: APLL2_EN = 1 → toggle soft reset → APLL2_EN = 0

Table 9-3 APLL2 LDO PSRR Performance
Frequency (kHz) Load (mA) VDD (V) Temperature (°C) PSRR (dB)
1 10 3.3 25 52
10 10 3.3 25 54
100 10 3.3 25 62
1 20 3.3 25 51
10 20 3.3 25 47
100 20 3.3 25 56
LMK5B12212 Supplying XO Input With CAP1_APLL2 Figure 9-3 Supplying XO Input With CAP1_APLL2