SNAS696C March   2017  – April 2019 LMX2594

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Requirements
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Reference Oscillator Input
      2. 7.3.2  Reference Path
        1. 7.3.2.1 OSCin Doubler (OSC_2X)
        2. 7.3.2.2 Pre-R Divider (PLL_R_PRE)
        3. 7.3.2.3 Programmable Multiplier (MULT)
        4. 7.3.2.4 Post-R Divider (PLL_R)
        5. 7.3.2.5 State Machine Clock
      3. 7.3.3  PLL Phase Detector and Charge Pump
      4. 7.3.4  N-Divider and Fractional Circuitry
      5. 7.3.5  MUXout Pin
        1. 7.3.5.1 Lock Detect
        2. 7.3.5.2 Readback
      6. 7.3.6  VCO (Voltage-Controlled Oscillator)
        1. 7.3.6.1 VCO Calibration
        2. 7.3.6.2 Determining the VCO Gain
      7. 7.3.7  Channel Divider
      8. 7.3.8  Output Buffer
      9. 7.3.9  Power-Down Modes
      10. 7.3.10 Phase Synchronization
        1. 7.3.10.1 General Concept
        2. 7.3.10.2 Categories of Applications for SYNC
        3. 7.3.10.3 Procedure for Using SYNC
        4. 7.3.10.4 SYNC Input Pin
      11. 7.3.11 Phase Adjust
      12. 7.3.12 Fine Adjustments for Phase Adjust and Phase SYNC
      13. 7.3.13 Ramping Function
        1. 7.3.13.1 Manual Pin Ramping
          1. 7.3.13.1.1 Manual Pin Ramping Example
        2. 7.3.13.2 Automatic Ramping
          1. 7.3.13.2.1 Automatic Ramping Example (Triangle Wave)
      14. 7.3.14 SYSREF
        1. 7.3.14.1 Programmable Fields
        2. 7.3.14.2 Input and Output Pin Formats
          1. 7.3.14.2.1 Input Format for SYNC and SysRefReq Pins
          2. 7.3.14.2.2 SYSREF Output Format
        3. 7.3.14.3 Examples
        4. 7.3.14.4 SYSREF Procedure
      15. 7.3.15 SysRefReq Pin
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 Recommended Initial Power-Up Sequence
      2. 7.5.2 Recommended Sequence for Changing Frequencies
      3. 7.5.3 General Programming Requirements
    6. 7.6 Register Maps
      1. 7.6.1  General Registers R0, R1, & R7
        1. Table 24. Field Descriptions
      2. 7.6.2  Input Path Registers
        1. Table 25. Field Descriptions
      3. 7.6.3  Charge Pump Registers (R13, R14)
        1. Table 26. Field Descriptions
      4. 7.6.4  VCO Calibration Registers
        1. Table 27. Field Descriptions
      5. 7.6.5  N Divider, MASH, and Output Registers
        1. Table 28. Field Descriptions
      6. 7.6.6  SYNC and SysRefReq Input Pin Register
        1. Table 29. Field Descriptions
      7. 7.6.7  Lock Detect Registers
        1. Table 30. Field Descriptions
      8. 7.6.8  MASH_RESET
        1. Table 31. Field Descriptions
      9. 7.6.9  SysREF Registers
        1. Table 32. Field Descriptions
      10. 7.6.10 CHANNEL Divider Registers
        1. Table 33. Field Descriptions
      11. 7.6.11 Ramping and Calibration Fields
        1. Table 34. Field Descriptions
      12. 7.6.12 Ramping Registers
        1. 7.6.12.1 Ramp Limits
          1. Table 35. Field Descriptions
        2. 7.6.12.2 Ramping Triggers, Burst Mode, and RAMP0_RST
          1. Table 36. Field Descriptions
        3. 7.6.12.3 Ramping Configuration
          1. Table 37. Field Descriptions
      13. 7.6.13 Readback Registers
        1. Table 38. Field Descriptions
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 OSCin Configuration
      2. 8.1.2 OSCin Slew Rate
      3. 8.1.3 RF Output Buffer Power Control
      4. 8.1.4 RF Output Buffer Pullup
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.1 Overview

The LMX2594 is a high-performance, wideband frequency synthesizer with integrated VCO and output divider. The VCO operates from 7.5 GHz to 15 GHz, and this can be combined with the output divider to produce any frequency in the range of 10 MHz to 15 GHz. Within the input path, there are two dividers and a multiplier for flexible frequency planning. The multiplier also allows the reduction of spurs by moving the frequencies away from the integer boundary.

The PLL is fractional-N PLL with a programmable delta-sigma modulator up to 4th order. The fractional denominator is a programmable 32-bit long, which can easily provide fine frequency steps below 1-Hz resolution, or be used to do exact fractions like 1/3, 7/1000, and many others. The phase frequency detector goes up to 300 MHz in fractional mode or 400 MHz in integer mode, although minimum N-divider values must also be taken into account.

For applications where deterministic or adjustable phase is desired, the SYNC pin can be used to get the phase relationship between the OSCin and RFout pins deterministic. When this is done, the phase can be adjusted in very fine steps of the VCO period divided by the fractional denominator.

The ultra-fast VCO calibration is designed for applications where the frequency must be swept or abruptly changed. The frequency can be manually programmed, or the device can be set up to do ramps and chirps.

The JESD204B support includes using the RFoutB output to create a differential SYSREF output that can be either a single pulse or a series of pulses that occur at a programmable distance away from the rising edges of the output signal.

The LMX2594 device requires only a single 3.3-V power supply. The internal power supplies are provided by integrated LDOs, eliminating the need for high-performance external LDOs.

The digital logic for the SPI interface and is compatible with voltage levels from 1.8 V to 3.3 V.

Table 1 shows the range of several of the dividers, multipliers, and fractional settings.

Table 1. Range of Dividers, Multipliers, and Fractional Settings

PARAMETER MIN MAX COMMENTS
Outputs enabled 0 2
OSCin doubler 0 (1X) 1 (2X) The low noise doubler can be used to increase the phase detector frequency to improve phase noise and avoid spurs. This is in reference to the OSC_2X bit.
Pre-R divider 1 (bypass) 128 Only use the Pre-R divider if the multiplier is used and the input frequency is too high for the multiplier.
Multiplier 3 7 This is in reference to the MULT word.
Post-R divider 1 (bypass) 255 The maximum input frequency for the Post-R divider is 250 MHz. Use the Pre-R divider if necessary.
N divider ≥ 28 524287 The minimum divide depends on modulator order and VCO frequency. See N-Divider and Fractional Circuitry for more details.
Fractional numerator/ denominator 1 (Integer mode) 232 – 1 = 4294967295 The fractional denominator is programmable and can assume any value between 1 and 232–1; it is not a fixed denominator.
Fractional order (MASH_ORDER) 0 4 Order 0 is integer mode and the order can be programmed
Channel divider 1 (bypass) 768 This is the series of several dividers. Also, be aware that above 10 GHz, the maximum allowable channel divider value is 6.
Output frequency 10 MHz 15 GHz This is implied by the minimum VCO frequency divided by the maximum channel divider value.