SNAS740B October   2017  – January 2019 LMX2572

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Functional Block Diagram
  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 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  Reference Oscillator Input
      2. 7.3.2  Reference Path
      3. 7.3.3  PLL Phase Detector and Charge Pump
      4. 7.3.4  PLL N Divider and Fractional Circuitry
      5. 7.3.5  Voltage-Controlled Oscillator
      6. 7.3.6  Channel Divider
      7. 7.3.7  Output Buffer
      8. 7.3.8  Lock Detect
      9. 7.3.9  Register Readback
      10. 7.3.10 Powerdown
      11. 7.3.11 Phase Synchronization
      12. 7.3.12 Phase Adjustment
      13. 7.3.13 Ramping Function
      14. 7.3.14 SYSREF
      15. 7.3.15 FSK Modulation
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 Recommended Initial Power-On Programming
        1. 7.5.1.1 Programming Sequence
        2. 7.5.1.2 Programming Register
      2. 7.5.2 Recommended Sequence for Changing Frequencies
      3. 7.5.3 Double Buffering
      4. 7.5.4 Block Programming
    6. 7.6 Register Maps
      1. 7.6.1   Register R0 (offset = 00h) [reset = 221Ch]
        1. Table 8. Register R0 Field Descriptions
      2. 7.6.2   Register R1 (offset = 01h) [reset = 0808h]
        1. Table 9. Register R1 Field Descriptions
      3. 7.6.3   Register R2 (offset = 02h) [reset = 0500h]
        1. Table 10. Register R2 Field Descriptions
      4. 7.6.4   Register R3 (offset = 03h) [reset = 0782h]
        1. Table 11. Register R3 Field Descriptions
      5. 7.6.5   Register R4 (offset = 04h) [reset = 0A43h]
        1. Table 12. Register R4 Field Descriptions
      6. 7.6.6   Register R5 (offset = 05h) [reset = 30C8h]
        1. Table 13. Register R5 Field Descriptions
      7. 7.6.7   Register R6 (offset = 06h) [reset = C802h]
        1. Table 14. Register R6 Field Descriptions
      8. 7.6.8   Register R7 (offset = 07h) [reset = 00B2h]
        1. Table 15. Register R7 Field Descriptions
      9. 7.6.9   Register R8 (offset = 08h) [reset = 2000h]
        1. Table 16. Register R8 Field Descriptions
      10. 7.6.10  Register R9 (offset = 09h) [reset = 0004h]
        1. Table 17. Register R9 Field Descriptions
      11. 7.6.11  Register R10 (offset = 0Ah) [reset = 10F8h]
        1. Table 18. Register R10 Field Descriptions
      12. 7.6.12  Register R11 (offset = 0Bh) [reset = B018h]
        1. Table 19. Register R11 Field Descriptions
      13. 7.6.13  Register R12 (offset = 0Ch) [reset = 5001h]
        1. Table 20. Register R12 Field Descriptions
      14. 7.6.14  Register R13 (offset = 0Dh) [reset = 4000h]
        1. Table 21. Register R13 Field Descriptions
      15. 7.6.15  Register R14 (offset = 0Eh) [reset = 1840h]
        1. Table 22. Register R14 Field Descriptions
      16. 7.6.16  Register R15 (offset = 0Fh) [reset = 060Eh]
        1. Table 23. Register R15 Field Descriptions
      17. 7.6.17  Register R16 (offset = 10h) [reset = 0080h]
        1. Table 24. Register R16 Field Descriptions
      18. 7.6.18  Register R17 (offset = 11h) [reset = 0096h]
        1. Table 25. Register R17 Field Descriptions
      19. 7.6.19  Register R18 (offset = 12h) [reset = 0064h]
        1. Table 26. Register R18 Field Descriptions
      20. 7.6.20  Register R19 (offset = 13h) [reset = 27B7h]
        1. Table 27. Register R19 Field Descriptions
      21. 7.6.21  Register R20 (offset = 14h) [reset = 3048h]
        1. Table 28. Register R20 Field Descriptions
      22. 7.6.22  Register R21 (offset = 15h) [reset = 0409h]
        1. Table 29. Register R21 Field Descriptions
      23. 7.6.23  Register R22 (offset = 16h) [reset = 0001h]
        1. Table 30. Register R22 Field Descriptions
      24. 7.6.24  Register R23 (offset = 17h) [reset = 007Ch]
        1. Table 31. Register R23 Field Descriptions
      25. 7.6.25  Register R24 (offset = 18h) [reset = 071Ah]
        1. Table 32. Register R24 Field Descriptions
      26. 7.6.26  Register R25 (offset = 19h) [reset = 0624h]
        1. Table 33. Register R25 Field Descriptions
      27. 7.6.27  Register R26 (offset = 1Ah) [reset = 0808h]
        1. Table 34. Register R26 Field Descriptions
      28. 7.6.28  Register R27 (offset = 1Bh) [reset = 0002h]
        1. Table 35. Register R27 Field Descriptions
      29. 7.6.29  Register R28 (offset = 1Ch) [reset = 0488h]
        1. Table 36. Register R28 Field Descriptions
      30. 7.6.30  Register R29 (offset = 1Dh) [reset = 18C6h]
        1. Table 37. Register R29 Field Descriptions
      31. 7.6.31  Register R30 (offset = 1Eh) [reset = 18C6h]
        1. Table 38. Register R30 Field Descriptions
      32. 7.6.32  Register R31 (offset = 1Fh) [reset = C3E6h]
        1. Table 39. Register R31 Field Descriptions
      33. 7.6.33  Register R32 (offset = 20h) [reset = 05BFh]
        1. Table 40. Register R32 Field Descriptions
      34. 7.6.34  Register R33 (offset = 21h) [reset = 1E01h]
        1. Table 41. Register R33 Field Descriptions
      35. 7.6.35  Register R34 (offset = 22h) [reset = 0010h]
        1. Table 42. Register R34 Field Descriptions
      36. 7.6.36  Register R35 (offset = 23h) [reset = 0004h]
        1. Table 43. Register R35 Field Descriptions
      37. 7.6.37  Register R36 (offset = 24h) [reset = 0028h]
        1. Table 44. Register R36 Field Descriptions
      38. 7.6.38  Register R37 (offset = 25h) [reset = 0205h]
        1. Table 45. Register R37 Field Descriptions
      39. 7.6.39  Register R38 (offset = 26h) [reset = FFFFh]
        1. Table 46. Register R38 Field Descriptions
      40. 7.6.40  Register R39 (offset = 27h) [reset = FFFFh]
        1. Table 47. Register R39 Field Descriptions
      41. 7.6.41  Register R40 (offset = 28h) [reset = 0000h]
        1. Table 48. Register R40 Field Descriptions
      42. 7.6.42  Register R41 (offset = 29h) [reset = 0000h]
        1. Table 49. Register R41 Field Descriptions
      43. 7.6.43  Register R42 (offset = 2Ah) [reset = 0000h]
        1. Table 50. Register R42 Field Descriptions
      44. 7.6.44  Register R43 (offset = 2Bh) [reset = 0000h]
        1. Table 51. Register R43 Field Descriptions
      45. 7.6.45  Register R44 (offset = 2Ch) [reset = 22A2h]
        1. Table 52. Register R44 Field Descriptions
      46. 7.6.46  Register R45 (offset = 2Dh) [reset = C622h]
        1. Table 53. Register R45 Field Descriptions
      47. 7.6.47  Register R46 (offset = 2Eh) [reset = 07F0h]
        1. Table 54. Register R46 Field Descriptions
      48. 7.6.48  Register R47 (offset = 2Fh) [reset = 0300h]
        1. Table 55. Register R47 Field Descriptions
      49. 7.6.49  Register R48 (offset = 30h) [reset = 03E0h]
        1. Table 56. Register R48 Field Descriptions
      50. 7.6.50  Register R49 (offset = 31h) [reset = 4180h]
        1. Table 57. Register R49 Field Descriptions
      51. 7.6.51  Register R50 (offset = 32h) [reset = 0080h]
        1. Table 58. Register R50 Field Descriptions
      52. 7.6.52  Register R51 (offset = 33h) [reset = 0080h]
        1. Table 59. Register R51 Field Descriptions
      53. 7.6.53  Register R52 (offset = 34h) [reset = 0420h]
        1. Table 60. Register R52 Field Descriptions
      54. 7.6.54  Register R53 (offset = 35h) [reset = 0000h]
        1. Table 61. Register R53 Field Descriptions
      55. 7.6.55  Register R54 (offset = 36h) [reset = 0000h]
        1. Table 62. Register R54 Field Descriptions
      56. 7.6.56  Register R55 (offset = 37h) [reset = 0000h]
        1. Table 63. Register R55 Field Descriptions
      57. 7.6.57  Register R56 (offset = 38h) [reset = 0000h]
        1. Table 64. Register R56 Field Descriptions
      58. 7.6.58  Register R57 (offset = 39h) [reset = 0000h]
        1. Table 65. Register R57 Field Descriptions
      59. 7.6.59  Register R58 (offset = 3Ah) [reset = 8001h]
        1. Table 66. Register R58 Field Descriptions
      60. 7.6.60  Register R59 (offset = 3Bh) [reset = 0001h]
        1. Table 67. Register R59 Field Descriptions
      61. 7.6.61  Register R60 (offset = 3Ch) [reset = 03E8h]
        1. Table 68. Register R60 Field Descriptions
      62. 7.6.62  Register R61 (offset = 3Dh) [reset = 00A8h]
        1. Table 69. Register R61 Field Descriptions
      63. 7.6.63  Register R62 (offset = 3Eh) [reset = 00AFh]
        1. Table 70. Register R62 Field Descriptions
      64. 7.6.64  Register R63 (offset = 3Fh) [reset = 0000h]
        1. Table 71. Register R63 Field Descriptions
      65. 7.6.65  Register R64 (offset = 40h) [reset = 1388h]
        1. Table 72. Register R64 Field Descriptions
      66. 7.6.66  Register R65 (offset = 41h) [reset = 0000h]
        1. Table 73. Register R65 Field Descriptions
      67. 7.6.67  Register R66 (offset = 42h) [reset = 01F4h]
        1. Table 74. Register R66 Field Descriptions
      68. 7.6.68  Register R67 (offset = 43h) [reset = 0000h]
        1. Table 75. Register R67 Field Descriptions
      69. 7.6.69  Register R68 (offset = 44h) [reset = 03E8h]
        1. Table 76. Register R68 Field Descriptions
      70. 7.6.70  Register R69 (offset = 45h) [reset = 0000h]
        1. Table 77. Register R69 Field Descriptions
      71. 7.6.71  Register R70 (offset = 46h) [reset = C350h]
        1. Table 78. Register R70 Field Descriptions
      72. 7.6.72  Register R71 (offset = 47h) [reset = 0080h]
        1. Table 79. Register R71 Field Descriptions
      73. 7.6.73  Register R72 (offset = 48h) [reset = 0001h]
        1. Table 80. Register R72 Field Descriptions
      74. 7.6.74  Register R73 (offset = 49h) [reset = 003Fh]
        1. Table 81. Register R73 Field Descriptions
      75. 7.6.75  Register R74 (offset = 4Ah) [reset = 0000h]
        1. Table 82. Register R74 Field Descriptions
      76. 7.6.76  Register R75 (offset = 4Bh) [reset = 0800h]
        1. Table 83. Register R75 Field Descriptions
      77. 7.6.77  Register R76 (offset = 4Ch) [reset = 000Ch]
        1. Table 84. Register R76 Field Descriptions
      78. 7.6.78  Register R77 (offset = 4Dh) [reset = 0000h]
        1. Table 85. Register R77 Field Descriptions
      79. 7.6.79  Register R78 (offset = 4Eh) [reset = 0064h]
        1. Table 86. Register R78 Field Descriptions
      80. 7.6.80  Register R79 (offset = 4Fh) [reset = 0000h]
        1. Table 87. Register R79 Field Descriptions
      81. 7.6.81  Register R80 (offset = 50h) [reset = 0000h]
        1. Table 88. Register R80 Field Descriptions
      82. 7.6.82  Register R81 (offset = 51h) [reset = 0000h]
        1. Table 89. Register R81 Field Descriptions
      83. 7.6.83  Register R82 (offset = 52h) [reset = 0000h]
        1. Table 90. Register R82 Field Descriptions
      84. 7.6.84  Register R83 (offset = 53h) [reset = 0000h]
        1. Table 91. Register R83 Field Descriptions
      85. 7.6.85  Register R84 (offset = 54h) [reset = 0000h]
        1. Table 92. Register R84 Field Descriptions
      86. 7.6.86  Register R85 (offset = 55h) [reset = 0000h]
        1. Table 93. Register R85 Field Descriptions
      87. 7.6.87  Register R86 (offset = 56h) [reset = 0000h]
        1. Table 94. Register R86 Field Descriptions
      88. 7.6.88  Register R87 (offset = 57h) [reset = 0000h]
        1. Table 95. Register R87 Field Descriptions
      89. 7.6.89  Register R88 (offset = 58h) [reset = 0000h]
        1. Table 96. Register R88 Field Descriptions
      90. 7.6.90  Register R89 (offset = 59h) [reset = 0000h]
        1. Table 97. Register R89 Field Descriptions
      91. 7.6.91  Register R90 (offset = 5Ah) [reset = 0000h]
        1. Table 98. Register R90 Field Descriptions
      92. 7.6.92  Register R91 (offset = 5Bh) [reset = 0000h]
        1. Table 99. Register R91 Field Descriptions
      93. 7.6.93  Register R92 (offset = 5Ch) [reset = 0000h]
        1. Table 100. Register R92 Field Descriptions
      94. 7.6.94  Register R93 (offset = 5Dh) [reset = 0000h]
        1. Table 101. Register R93 Field Descriptions
      95. 7.6.95  Register R94 (offset = 5Eh) [reset = 0000h]
        1. Table 102. Register R94 Field Descriptions
      96. 7.6.96  Register R95 (offset = 5Fh) [reset = 0000h]
        1. Table 103. Register R95 Field Descriptions
      97. 7.6.97  Register R96 (offset = 60h) [reset = 0000h]
        1. Table 104. Register R96 Field Descriptions
      98. 7.6.98  Register R97 (offset = 61h) [reset = 0000h]
        1. Table 105. Register R97 Field Descriptions
      99. 7.6.99  Register R98 (offset = 62h) [reset = 0000h]
        1. Table 106. Register R98 Field Descriptions
      100. 7.6.100 Register R99 (offset = 63h) [reset = 0000h]
        1. Table 107. Register R99 Field Descriptions
      101. 7.6.101 Register R100 (offset = 64h) [reset = 0000h]
        1. Table 108. Register R100 Field Descriptions
      102. 7.6.102 Register R101 (offset = 65h) [reset = 0000h]
        1. Table 109. Register R101 Field Descriptions
      103. 7.6.103 Register R102 (offset = 66h) [reset = 0000h]
        1. Table 110. Register R102 Field Descriptions
      104. 7.6.104 Register R103 (offset = 67h) [reset = 0000h]
        1. Table 111. Register R103 Field Descriptions
      105. 7.6.105 Register R104 (offset = 68h) [reset = 0000h]
        1. Table 112. Register R104 Field Descriptions
      106. 7.6.106 Register R105 (offset = 69h) [reset = 4440h]
        1. Table 113. Register R105 Field Descriptions
      107. 7.6.107 Register R106 (offset = 6Ah) [reset = 0007h]
        1. Table 114. Register R106 Field Descriptions
      108. 7.6.108 Register R107 (offset = 6Bh) [reset = 0000h]
        1. Table 115. Register R107 Field Descriptions
      109. 7.6.109 Register R108 (offset = 6Ch) [reset = 0000h]
        1. Table 116. Register R108 Field Descriptions
      110. 7.6.110 Register R109 (offset = 6Dh) [reset = 0000h]
        1. Table 117. Register R109 Field Descriptions
      111. 7.6.111 Register R110 (offset = 6Eh) [reset = 0000h]
        1. Table 118. Register R110 Field Descriptions
      112. 7.6.112 Register R111 (offset = 6Fh) [reset = 0000h]
        1. Table 119. Register R111 Field Descriptions
      113. 7.6.113 Register R112 (offset = 70h) [reset = 0000h]
        1. Table 120. Register R112 Field Descriptions
      114. 7.6.114 Register R113 (offset = 71h) [reset = 0000h]
        1. Table 121. Register R113 Field Descriptions
      115. 7.6.115 Register R114 (offset = 72h) [reset = 7800h]
        1. Table 122. Register R114 Field Descriptions
      116. 7.6.116 Register R115 (offset = 73h) [reset = 0000h]
        1. Table 123. Register R115 Field Descriptions
      117. 7.6.117 Register R116 (offset = 74h) [reset = 0000h]
        1. Table 124. Register R116 Field Descriptions
      118. 7.6.118 Register R117 (offset = 75h) [reset = 0000h]
        1. Table 125. Register R117 Field Descriptions
      119. 7.6.119 Register R118 (offset = 76h) [reset = 0000h]
        1. Table 126. Register R118 Field Descriptions
      120. 7.6.120 Register R119 (offset = 77h) [reset = 0000h]
        1. Table 127. Register R119 Field Descriptions
      121. 7.6.121 Register R120 (offset = 78h) [reset = 0000h]
        1. Table 128. Register R120 Field Descriptions
      122. 7.6.122 Register R121 (offset = 79h) [reset = 0000h]
        1. Table 129. Register R121 Field Descriptions
      123. 7.6.123 Register R122 (offset = 7Ah) [reset = 0000h]
        1. Table 130. Register R122 Field Descriptions
      124. 7.6.124 Register R123 (offset = 7Bh) [reset = 0000h]
        1. Table 131. Register R123 Field Descriptions
      125. 7.6.125 Register R124 (offset = 7Ch) [reset = 0000h]
        1. Table 132. Register R124 Field Descriptions
      126. 7.6.126 Register R125 (offset = 7Dh) [reset = 2288h]
        1. Table 133. Register R125 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  VCO Gain
      4. 8.1.4  VCO Calibration
        1. 8.1.4.1 Partial Assist
        2. 8.1.4.2 Close Frequency Assist
        3. 8.1.4.3 Full Assist
      5. 8.1.5  Output Buffer Control
        1. 8.1.5.1 Output Power
        2. 8.1.5.2 Power-Up Response
        3. 8.1.5.3 Unused Output Pin
      6. 8.1.6  Application for SYNC
      7. 8.1.7  Application for Ramp
        1. 8.1.7.1 Manual Ramping Mode
        2. 8.1.7.2 Automatic Ramping Mode
      8. 8.1.8  Application for SYSREF
        1. 8.1.8.1 Driving SysRefReq Pin With Differential Signal
        2. 8.1.8.2 SYSREF Output
      9. 8.1.9  Application for FSK
      10. 8.1.10 Unused Pins
      11. 8.1.11 External Loop Filter
      12. 8.1.12 Power-Up, Wake-Up Time
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 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 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.3.2 Reference Path

The reference path consists of an OSCin doubler (OSC_2X), Pre-R divider (PLL_R_PRE), Multiplier (MULT), and a Post-R divider (PLL_R).

LMX2572 RefPath-SNAS740.gifFigure 31. Reference Path

The Doubler allows one to double the input reference frequency up to 250 MHz. The Doubler adds minimal noise and is useful for raising the phase detector frequency for better phase noise. The Doubler can also be used to avoid spurs. The Doubler uses both the rising and falling edges of the input signal, so the input signal must have 50% duty cycle if the Doubler is enabled. Note that the Multiplier cannot be used if the Doubler is engaged.

The Pre-R divider can help reduce input frequency so that the Multiplier can be used and the maximum 200-MHz input frequency limitation of the Post-R divider can be met.

The Multiplier multiplies the frequency up under the allowable multiplications of 3, 4, 5, 6, and 7. In combination with the Pre-R and Post-R dividers, the Multiplier offers the flexibility to shift the phase detector frequency away from frequencies that may create integer boundary spurs with the VCO and the output frequencies. Be aware that unlike the Doubler, the Multiplier degrades the PLL figure of merit. This degradation would only matter, however, for a very clean reference oscillator input and if the loop bandwidth was wide. The user should not use the Doubler while using the Multiplier. The Multiplier is bypassed if its value is set to 1.

The Post-R divider can be used to further divide down the frequency to the phase detector frequency. When it is used (PLL_R > 1), the input frequency to this divider is limited to 200 MHz.

Use Equation 1 to calculate the phase detector frequency, fPD.

Equation 1. fPD = fOSCin × OSC_2X × MULT / (PLL_R_PRE × PLL_R)

Table 1 summarizes the usage boundaries of these functional blocks in the reference path.

Table 1. Reference Path Boundaries

PARAMETER VALUE INPUT FREQUENCY (MHz) OUTPUT FREQUENCY (MHz) NOTES
MIN MAX MIN MAX
OSCin N/A 5 250
Doubler 0 (Bypassed), 1 (x2) 5 125 10 250 When OSC_2X = 1, Multiplier cannot be used at the same time.
Pre-R divider 1 (Bypassed), 2, 3, …, 254, 255 5 200 0.25 200 Keep it equals 1 unless when necessary.
Multiplier 1 (Bypassed), 3, 4, 5, 6, 7 10 40 60 150 When the output frequency is greater than 100MHz, set MULT_HI = 1.
Post-R divider 1 (Bypass), 2, 3, …, 254, 255 5 200 0.25 200