SNAS824B October   2021  – June 2022 LMX2571-EP

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 Timing Diagrams
    8. 6.8 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  Differences Between the LMX2571 and LMX2571-EP
      2. 7.3.2  Reference Oscillator Input
      3. 7.3.3  R-Dividers and Multiplier
      4. 7.3.4  PLL Phase Detector and Charge Pump
        1. 7.3.4.1 CPout Pin Charge Pump Current
        2. 7.3.4.2 Charge Pump Current When Using External VCO
      5. 7.3.5  PLL N-Divider and Fractional Circuitry
      6. 7.3.6  Partially Integrated Loop Filter
      7. 7.3.7  Low-Noise, Fully Integrated VCO
      8. 7.3.8  External VCO Support
      9. 7.3.9  Programmable RF Output Divider
      10. 7.3.10 Programmable RF Output Buffer
      11. 7.3.11 Integrated TX, RX Switch
      12. 7.3.12 Power Down
      13. 7.3.13 Lock Detect
      14. 7.3.14 FSK Modulation
      15. 7.3.15 FastLock
      16. 7.3.16 Register Readback
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation Mode
      2. 7.4.2 Duplex Mode
      3. 7.4.3 FSK Mode
    5. 7.5 Programming
      1. 7.5.1 Recommended Initial Power on Programming Sequence
      2. 7.5.2 Recommended Sequence for Changing Frequencies
    6. 7.6 Register Maps
      1. 7.6.1  R60 Register (offset = 3Ch) [reset = 4000h]
      2. 7.6.2  R58 Register (offset = 3Ah) [reset = C00h]
      3. 7.6.3  R53 Register (offset = 35h) [reset = 2802h]
      4. 7.6.4  R47 Register (offset = 2Fh) [reset = 0h]
      5. 7.6.5  R46 Register (offset = 2Eh) [reset = 1Ah]
      6. 7.6.6  R42 Register (offset = 2Ah) [reset = 210h]
      7. 7.6.7  R41 Register (offset = 29h) [reset = 810h]
      8. 7.6.8  R40 Register (offset = 28h) [reset = 101Ch]
      9. 7.6.9  R39 Register (offset = 27h) [reset = 11F0h]
      10. 7.6.10 R35 Register (offset = 23h) [reset = 647h]
      11. 7.6.11 R34 Register (offset = 22h) [reset = 1000h]
      12. 7.6.12 R33 Register (offset = 21h) [reset = 0h]
      13. 7.6.13 R25 to R32 Register (offset = 19h to 20h) [reset = 0h]
      14. 7.6.14 R24 Register (offset = 18h) [reset = 10h]
      15. 7.6.15 R23 Register (offset = 17h) [reset = 10A4h]
      16. 7.6.16 R22 Register (offset = 16h) [reset = 8584h]
      17. 7.6.17 R21 Register (offset = 15h) [reset = 101h]
      18. 7.6.18 R20 Register (offset = 14h) [reset = 28h]
      19. 7.6.19 R19 Register (offset = 13h) [reset = 0h]
      20. 7.6.20 R18 Register (offset = 12h) [reset = 0h]
      21. 7.6.21 R17 Register (offset = 11h) [reset = 0h]
      22. 7.6.22 R9 to R16 Register (offset = 9h to 10h) [reset = 0h]
      23. 7.6.23 R8 Register (offset = 8h) [reset = 10h]
      24. 7.6.24 R7 Register (offset = 7h) [reset = 10A4h]
      25. 7.6.25 R6 Register (offset = 6h) [reset = 8584h]
      26. 7.6.26 R5 Register (offset = 5h) [reset = 101h]
      27. 7.6.27 R4 Register (offset = 4h) [reset = 28h]
      28. 7.6.28 R3 Register (offset = 3h) [reset = 0h]
      29. 7.6.29 R2 Register (offset = 2h) [reset = 0h]
      30. 7.6.30 R1 Register (offset = 1h) [reset = 0h]
      31. 7.6.31 R0 Register (offset = 0h) [reset = 3h]
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Direct Digital FSK Modulation
      2. 8.1.2  Frequency and Output Port Switching
      3. 8.1.3  OSCin Configuration
      4. 8.1.4  Register R0 F1F2_INIT, F1F2_MODE Usage
      5. 8.1.5  FastLock With External VCO
      6. 8.1.6  OSCin Slew Rate
      7. 8.1.7  RF Output Buffer Power Control
      8. 8.1.8  RF Output Buffer Type
      9. 8.1.9  MULT Multiplier
      10. 8.1.10 Integrated VCO
    2. 8.2 Typical Applications
      1. 8.2.1 Synthesizer Duplex Mode
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Synthesizer Duplex Mode Application Curves
      2. 8.2.2 PLL Duplex Mode
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 PLL Duplex Mode Application Curves
      3. 8.2.3 Synthesizer/PLL Duplex Mode
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
        3. 8.2.3.3 Synthesizer/PLL Duplex Mode Application Curves
    3. 8.3 Do's and Don'ts
  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 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.15 FastLock

The LMX2571-EP includes a FastLock feature that can be used to improve the lock times in PLL mode when the loop bandwidth is small. In general, the lock time is approximately equal to 4 divided by the loop bandwidth. If the loop bandwidth is 1 kHz, then the lock time would be 4 ms. However, if the fPD is much higher than the loop bandwidth, cycle slipping may occur, and the actual lock time will be much longer. Traditional fastlock usually reduces lock time by increasing loop bandwidth during frequency switching. However, there is a limitation on the achievable maximum loop bandwidth due to limitation on charge-pump current and loop filter component values. In some cases, this kind of fastlock technique will make cycle slip even worse.

The LMX2571-EP adopts a new FastLock approach that eliminates the cycle slip problem. With an external analog SPST switch in conjunction with FastLock control of the LMX2571-EP, the lock time for a 100-MHz frequency switch could be settled in less than 1.5 ms. See Section 8.1.5 for details.