SNAS739D June   2018  – May 2020 LMX2615-SP

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
      1.      CQFP Package (QFN) 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 Post-R Divider (PLL_R)
      3. 7.3.3  State Machine Clock
      4. 7.3.4  PLL Phase Detector and Charge Pump
      5. 7.3.5  N Divider and Fractional Circuitry
      6. 7.3.6  MUXout Pin
        1. 7.3.6.1 Serial Data Output for Readback
        2. 7.3.6.2 Lock Detect Indicator Set as Type “VCOCal”
        3. 7.3.6.3 Lock Detect Indicator Set as Type “Vtune and VCOCal”
      7. 7.3.7  VCO (Voltage-Controlled Oscillator)
        1. 7.3.7.1 VCO Calibration
        2. 7.3.7.2 Watchdog Feature
        3. 7.3.7.3 RECAL Feature
        4. 7.3.7.4 Determining the VCO Gain
      8. 7.3.8  Channel Divider
      9. 7.3.9  Output Buffer
      10. 7.3.10 Powerdown Modes
      11. 7.3.11 Treatment of Unused Pins
      12. 7.3.12 Phase Synchronization
        1. 7.3.12.1 General Concept
        2. 7.3.12.2 Categories of Applications for SYNC
        3. 7.3.12.3 Procedure for Using SYNC
        4. 7.3.12.4 SYNC Input Pin
      13. 7.3.13 Phase Adjust
      14. 7.3.14 Fine Adjustments for Phase Adjust and Phase SYNC
      15. 7.3.15 SYSREF
        1. 7.3.15.1 Programmable Fields
        2. 7.3.15.2 Input and Output Pin Formats
          1. 7.3.15.2.1 SYSREF Output Format
        3. 7.3.15.3 Examples
        4. 7.3.15.4 SYSREF Procedure
      16. 7.3.16 Pin Modes
    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
    6. 7.6 Register Maps
      1. 7.6.1 Register Map
        1. 7.6.1.1  R0 Register (Offset = 0x0) [reset = X]
          1. Table 22. R0 Register Field Descriptions
        2. 7.6.1.2  R1 Register (Offset = 0x1) [reset = 0x4]
          1. Table 23. R1 Register Field Descriptions
        3. 7.6.1.3  R8 Register (Offset = 0x8) [reset = X]
          1. Table 24. R8 Register Field Descriptions
        4. 7.6.1.4  R9 Register (Offset = 0x9) [reset = X]
          1. Table 25. R9 Register Field Descriptions
        5. 7.6.1.5  R11 Register (Offset = 0xB) [reset = 0x10]
          1. Table 26. R11 Register Field Descriptions
        6. 7.6.1.6  R12 Register (Offset = 0xC) [reset = 0x1]
          1. Table 27. R12 Register Field Descriptions
        7. 7.6.1.7  R14 Register (Offset = 0xE) [reset = 0x70]
          1. Table 28. R14 Register Field Descriptions
        8. 7.6.1.8  R16 Register (Offset = 0x10) [reset = 0x80]
          1. Table 29. R16 Register Field Descriptions
        9. 7.6.1.9  R19 Register (Offset = 0x13) [reset = 0xB7]
          1. Table 30. R19 Register Field Descriptions
        10. 7.6.1.10 R20 Register (Offset = 0x14) [reset = X]
          1. Table 31. R20 Register Field Descriptions
        11. 7.6.1.11 R31 Register (Offset = 0x1F) [reset = X]
          1. Table 32. R31 Register Field Descriptions
        12. 7.6.1.12 R34 Register (Offset = 0x22) [reset = 0x0]
          1. Table 33. R34 Register Field Descriptions
        13. 7.6.1.13 R36 Register (Offset = 0x24) [reset = 0x46]
          1. Table 34. R36 Register Field Descriptions
        14. 7.6.1.14 R37 Register (Offset = 0x25) [reset = 0x400]
          1. Table 35. R37 Register Field Descriptions
        15. 7.6.1.15 R38 Register (Offset = 0x26) [reset = 0xFD51]
          1. Table 36. R38 Register Field Descriptions
        16. 7.6.1.16 R39 Register (Offset = 0x27) [reset = 0xDA80]
          1. Table 37. R39 Register Field Descriptions
        17. 7.6.1.17 R40 Register (Offset = 0x28) [reset = 0x0]
          1. Table 38. R40 Register Field Descriptions
        18. 7.6.1.18 R41 Register (Offset = 0x29) [reset = 0x0]
          1. Table 39. R41 Register Field Descriptions
        19. 7.6.1.19 R42 Register (Offset = 0x2A) [reset = 0x0]
          1. Table 40. R42 Register Field Descriptions
        20. 7.6.1.20 R43 Register (Offset = 0x2B) [reset = 0x0]
          1. Table 41. R43 Register Field Descriptions
        21. 7.6.1.21 R44 Register (Offset = 0x2C) [reset = 0x1FA3]
          1. Table 42. R44 Register Field Descriptions
        22. 7.6.1.22 R45 Register (Offset = 0x2D) [reset = X]
          1. Table 43. R45 Register Field Descriptions
        23. 7.6.1.23 R46 Register (Offset = 0x2E) [reset = 0x1]
          1. Table 44. R46 Register Field Descriptions
        24. 7.6.1.24 R58 Register (Offset = 0x3A) [reset = X]
          1. Table 45. R58 Register Field Descriptions
        25. 7.6.1.25 R59 Register (Offset = 0x3B) [reset = 0x1]
          1. Table 46. R59 Register Field Descriptions
        26. 7.6.1.26 R60 Register (Offset = 0x3C) [reset = 0x9C4]
          1. Table 47. R60 Register Field Descriptions
        27. 7.6.1.27 R69 Register (Offset = 0x45) [reset = 0x0]
          1. Table 48. R69 Register Field Descriptions
        28. 7.6.1.28 R70 Register (Offset = 0x46) [reset = 0xC350]
          1. Table 49. R70 Register Field Descriptions
        29. 7.6.1.29 R71 Register (Offset = 0x47) [reset = 0x80]
          1. Table 50. R71 Register Field Descriptions
        30. 7.6.1.30 R72 Register (Offset = 0x48) [reset = 0x1]
          1. Table 51. R72 Register Field Descriptions
        31. 7.6.1.31 R73 Register (Offset = 0x49) [reset = 0x3F]
          1. Table 52. R73 Register Field Descriptions
        32. 7.6.1.32 R74 Register (Offset = 0x4A) [reset = 0x0]
          1. Table 53. R74 Register Field Descriptions
        33. 7.6.1.33 R75 Register (Offset = 0x4B) [reset = 0x0]
          1. Table 54. R75 Register Field Descriptions
        34. 7.6.1.34 R110 Register (Offset = 0x6E) [reset = 0x0]
          1. Table 55. R110 Register Field Descriptions
        35. 7.6.1.35 R111 Register (Offset = 0x6F) [reset = 0x0]
          1. Table 56. R111 Register Field Descriptions
        36. 7.6.1.36 R112 Register (Offset = 0x70) [reset = 0x0]
          1. Table 57. R112 Register Field Descriptions
        37. 7.6.1.37 R113 Register (Offset = 0x71) [reset = 0x0]
          1. Table 58. R113 Register Field Descriptions
        38. 7.6.1.38 R114 Register (Offset = 0x72) [reset = 0x26F]
          1. Table 59. R114 Register 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
        1. 8.1.4.1 Resistor Pullup
        2. 8.1.4.2 Inductor Pullup
        3. 8.1.4.3 Combination Pullup
      5. 8.1.5 RF Output Treatment for the Complimentary Side
        1. 8.1.5.1 Single-Ended Termination of Unused Output
        2. 8.1.5.2 Differential Termination
    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
    3. 10.3 Footprint Example on PCB Layout
    4. 10.4 Radiation Environments
      1. 10.4.1 Total Ionizing Dose
      2. 10.4.2 Single Event Effect
  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 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Engineering Samples
    2. 12.2 Package Mechanical Information

Package Options

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

8.1.4.2 Inductor Pullup

Another strategy is to choose an inductor pullup (L). This allows a higher impedance without any concern of creating any DC drop across the component. Ideally, the inductor should be chosen large enough so that the impedance is high relative to the load impedance and also be operating away from its self-resonant frequency. For instance, consider a 3.3 nH pullup inductor with a self-resonant frequency of 7 GHz driving a 25-Ω spectrum analyzer input. This inductor theoretically has j50-Ω input impedance around 2.4 GHz. At this frequency, this in parallel with load is about j35-Ω, which is a 3 dB power reduction. At 1.4 GHz, this inductor has impedance of about 29-Ω. This in parallel with the 50-Ω load has a magnitude of 25-Ω, which is the same as you would get with the 50-Ω pullup. The main issue with the inductor pullup is the impedance does not look nicely matched to the load.

LMX2615-SP ai_output_ind_snas696.gifFigure 71. Inductor Pullup

As the output impedance is not so nicely matched, but there is higher output power, it makes sense to use a resistive pad to get the best impedance control. A 6-dB pad (R1 = 18 Ω, R2 = 68 Ω) is likely more attenuation than necessary. A 3-dB or even 1-dB pad might suffice. Two AC-coupling capacitor is required before the pad. In the configuration shown in Figure 72, one of them is placed by the resistor to ground to minimize the number of components in the high frequency path for lower loss.

LMX2615-SP schem_PullUpPad.gifFigure 72. Inductor Pullup With Pad

For the resistive pad, Table 61 shows some common values:

Table 61. Resistive T-Pad Values

ATTENUATION R1 R2
1 dB 2.7 Ω 420 Ω
2 dB 5.6 Ω 220 Ω
3 dB 6.8 Ω 150 Ω
4 dB 12 Ω 100 Ω
5 dB 15 Ω 82 Ω
6 dB 18 Ω 68 Ω