SNAS850 December   2024 LMX1205

ADVANCE INFORMATION  

  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 Timing Requirements
    7. 5.7 Timing Diagram
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
      1. 6.1.1 Range of Dividers and Multiplier
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Power On Reset
      2. 6.3.2 Temperature Sensor
      3. 6.3.3 Clock Input
        1. 6.3.3.1 Clock Input Adjustable Delay
      4. 6.3.4 Clock Outputs
        1. 6.3.4.1 Clock Output Buffers
        2. 6.3.4.2 Clock Output Adjustable Delay
        3. 6.3.4.3 Clock MUX
        4. 6.3.4.4 Clock Divider
        5. 6.3.4.5 Clock Multiplier
          1. 6.3.4.5.1 General Information About the Clock Multiplier
          2. 6.3.4.5.2 State Machine Clock for the Clock Multiplier
            1. 6.3.4.5.2.1 State Machine Clock
          3. 6.3.4.5.3 Calibration for the Clock Multiplier
          4. 6.3.4.5.4 Lock Detect for the Clock Multiplier
      5. 6.3.5 LOGICLK Outputs
        1. 6.3.5.1 LOGICLK Output Format
        2. 6.3.5.2 LOGICLK Dividers
      6. 6.3.6 SYSREF
        1. 6.3.6.1 SYSREF Output Buffers
          1. 6.3.6.1.1 SYSREF Output Buffers for Main Clocks (SYSREFOUT)
          2. 6.3.6.1.2 LOGISYSREF Output Buffer
          3. 6.3.6.1.3 SYSREF Frequency and Delay Generation
          4. 6.3.6.1.4 SYSREFREQ Pins and SYSREFREQ SPI Controlled Fields
            1. 6.3.6.1.4.1 SYSREFREQ Pins Common-Mode Voltage
            2. 6.3.6.1.4.2 SYSREFREQ Windowing Feature
              1. 6.3.6.1.4.2.1 General Procedure Flowchart for SYSREF Windowing Operation
              2. 6.3.6.1.4.2.2 Other Guidance For SYSREF Windowing
              3. 6.3.6.1.4.2.3 For Glitch-Free Output
              4. 6.3.6.1.4.2.4 If Using SYNC Feature
              5. 6.3.6.1.4.2.5 SYNC Feature
      7. 6.3.7 Power-Up Timing
      8. 6.3.8 Treatment of Unused Pins
    4. 6.4 Device Functional Modes Configurations
  8. 7 Register Map
    1. 7.1 Device Registers
  9. 8 Application and Implementation
    1. 8.1 Reference
      1. 8.1.1 Typical Application
        1. 8.1.1.1 Design Requirements
        2. 8.1.1.2 Detailed Design Procedure
        3. 8.1.1.3 Application Plots
    2. 8.2 Power Supply Recommendations
    3. 8.3 Layout
      1. 8.3.1 Layout Guidelines
      2. 8.3.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

6.3.6 SYSREF

SYSREF allows a low frequency JESD204B/C compliant signal to be produced that is reclocked to a main clock outputs or LOGICLK outputs. The delays between the CLKOUT and SYSREF outputs are adjustable with software. The SYSREF output can be configured as a generator using the internal SYSREF divider, or as a repeater duplicating the signal on the SYSREFREQ pins. The SYSREF generator for both the main clocks and the LOGICLK output are the same.

Table 6-9 SYSREF Modes
SYSREF_MODE DESCRIPTION
0 Generator Mode

Internal generator creates a continuous stream of SYSREF pulses. The SYSREFREQ_INPUT bits setting used to gate the SYSREF divider through SYSREFREQ pins or logic high from the channels for improved noise isolation without disrupting the synchronization of the SYSREF dividers. The SYSREFREQ_INPUT bits must be set for SYSREFREQ pins input or force high with changing bit from SYSREFREQ_INPUT[1] → 0 to 1 for a SYSREF output to come out.
1 Pulser

Internal generator generates a burst of 1 - 16 pulses that is set by SYSREF_PULSE_CNT that occurs with the SYSREFREQ_INPUT settings for rising edge on the SYSREFREQ pins or force high with changing bit from SYSREFREQ_INPUT[1] → 0 to 1
2 Repeater Mode

SYSREFREQ pins input are bypass to the SYSREFOUT outputs pins. If the delay is needed, the SYSREFREQ pins input are reclocked to clock outputs accordance to the SYSREF_DLY_BYP field before sent to the SYSREFOUT output pins.
3 Repeater Retime Mode

SYSREFREQ pins input are reclocked to clock input and then delayed in accordance to the SYSREF_DLY_BYP field before sent to the SYSREFOUT output pins.
Below figures show the functional block diagrams for different SYSREF modes.
LMX1205 Functional Block Diagram of SYSREF Circuitry in Generator Mode Figure 6-4 Functional Block Diagram of SYSREF Circuitry in Generator Mode
LMX1205 Functional Block Diagram of SYSREF Circuitry in Pulser Mode Figure 6-5 Functional Block Diagram of SYSREF Circuitry in Pulser Mode
LMX1205 Functional Block Diagram of SYSREF Circuitry in Repeater Mode Figure 6-6 Functional Block Diagram of SYSREF Circuitry in Repeater Mode
LMX1205 Functional Block Diagram of SYSREF Circuitry in Repeater Retime Mode Figure 6-7 Functional Block Diagram of SYSREF Circuitry in Repeater Retime Mode