SNAU308A November   2024  – May 2025

 

  1.   1
  2.   Description
  3.   Get Started
  4.   Features
  5.   Applications
  6.   6
  7. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
  8. 2Hardware
    1. 2.1 Setup
      1. 2.1.1 Evaluation Setup Requirement
      2. 2.1.2 Connection Diagram
    2. 2.2 Jumper Information
    3. 2.3 Power Requirements
    4. 2.4 Reference Clock
    5. 2.5 Output Connections
    6. 2.6 Test Points
  9. 3Software
    1. 3.1 Software Description
    2. 3.2 Software Installation
    3. 3.3 USB2ANY Interface
  10. 4Implementation Results
    1. 4.1 Evaluation Setup
    2. 4.2 Performance Data and Results
      1. 4.2.1 RF Output
      2. 4.2.2 VCO Calibration
        1. 4.2.2.1 No Assist Operation
        2. 4.2.2.2 Full Assist Operation
      3. 4.2.3 SYSREF
        1. 4.2.3.1 SYSREF Clock Generation
        2. 4.2.3.2 SYSREF Pulse Generation
        3. 4.2.3.3 SYSREF Repeater Mode
      4. 4.2.4 Phase Adjustment
      5. 4.2.5 Phase Synchronization
        1. 4.2.5.1 Category 1b and Category 2 SYNC
        2. 4.2.5.2 Category 3 SYNC
      6. 4.2.6 Pin Mode
  11. 5Hardware Design Files
    1. 5.1 Schematics
    2. 5.2 PCB Layouts
    3. 5.3 Bill of Materials (BOM)
  12. 6Additional Information
    1. 6.1 Debug Information
    2. 6.2 Trademarks
  13. 7Revision History

4.2.2.2 Full Assist Operation

Every time the VCO frequency is changed, instead of performing a VCO calibration, Full Assist operation specifies the VCO core and band for the PLL to lock. As a result, there is no VCO calibration time involved. The total time taken to switch VCO frequency is equal to register programming time plus PLL lock time.

To be able to know which VCO core and band to use for a specific VCO frequency, a one-time VCO calibration needs to be performed, a register read back needs to be performed to collect this information, and the information needs to be stored in a look up table (LUT). In addition to the VCO parameters, if VCO doubler is used, VCO doubler parameters can be obtained in the similar fashion. For example, again switching the VCO frequency between 7500MHz and 15GHz. RFOUTA is divide by 4 output. With Full Assist operation, the lock time (excluding register programming time) is less than 20µs.

LMX2624SPEVM LMX2695SEPEVM LMX2824EPEVM Full Assist Jump DownFigure 4-16 Full Assist Jump Down
LMX2624SPEVM LMX2695SEPEVM LMX2824EPEVM Full Assist Jump UpFigure 4-17 Full Assist Jump Up
Programming information:

A. LUT creation

  1. Set MUXOUT = Register read back.
  2. Set READBACK = Read state machine value.
  3. Program the LMX device to lock to 7500MHz with No Assist operation.
  4. Click the Register read back button once to read back the register values as shown in the Full assist read back column. Record these values in a text file.
  5. Repeat step 3 to 4 for 15GHz.
LMX2624SPEVM LMX2695SEPEVM LMX2824EPEVM LUT CreationFigure 4-18 LUT Creation
LMX2624SPEVM LMX2695SEPEVM LMX2824EPEVM Full Assist ProgrammingFigure 4-19 Full Assist Programming

B. Apply LUT data

  1. Set VCO_FULL_ASSIST = 1.
  2. Set DBL_BUF_EN = 1.
  3. Program PFD_DLY, PLL_N, PLL_NUM for VCO = 7500MHz.
  4. Program VCO_SEL, VCO_DACISET and VCO_CAPCTRL with the values from LUT.
  5. Click Calibrate VCO button once to kick start VCO switching. (Use the CSB pin to trigger test equipment)
  6. Repeat step 3 to 4 for VCO = 15000MHz.
  7. Click Calibrate VCO button once to kick start VCO switching. (Use the CSB pin to trigger test equipment)