SNAS783C June   2020  – February 2021 LMX2820

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 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  Input Path
        1. 7.3.2.1 Input Path Doubler (OSC_2X)
        2. 7.3.2.2 Pre-R Divider (PLL_R_PRE)
        3. 7.3.2.3 Programmable Input Multiplier (MULT)
        4. 7.3.2.4 R Divider (PLL_R)
      3. 7.3.3  PLL Phase Detector and Charge Pump
      4. 7.3.4  N Divider and Fractional Circuitry
        1. 7.3.4.1 Integer N Divide Portion (PLL_N)
        2. 7.3.4.2 Fractional N Divide Portion (PLL_NUM and PLL_DEN)
        3. 7.3.4.3 Modulator Order (MASH_ORDER)
      5. 7.3.5  LD Pin Lock Detect
      6. 7.3.6  MUXOUT Pin and Readback
      7. 7.3.7  Internal VCO
        1. 7.3.7.1 VCO Calibration
          1. 7.3.7.1.1 Determining the VCO Gain and Ranges
      8. 7.3.8  Channel Divider
      9. 7.3.9  Output Frequency Doubler
      10. 7.3.10 Output Buffer
      11. 7.3.11 Power-Down Modes
      12. 7.3.12 Phase Synchronization for Multiple Devices
        1. 7.3.12.1 SYNC Categories
        2. 7.3.12.2 Phase Adjust
          1. 7.3.12.2.1 Using MASH_SEED to Create a Phase Shift
          2. 7.3.12.2.2 Static vs. Dynamic Phase Adjust
          3. 7.3.12.2.3 Fine Adjustments to Phase Adjust
      13. 7.3.13 SYSREF
      14. 7.3.14 Fast VCO Calibration
      15. 7.3.15 Double Buffering (Shadow Registers)
      16. 7.3.16 Output Mute Pin and Ping Pong Approaches
    4. 7.4 Device Functional Modes
      1. 7.4.1 External VCO Mode
      2. 7.4.2 External Feedback Input Pins
        1. 7.4.2.1 PFDIN External Feedback Mode
        2. 7.4.2.2 RFIN External Feedback Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Treatment of Unused Pins
      2. 8.1.2 External Loop Filter
      3. 8.1.3 Using Instant Calibration
    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 Initialization and Power-on Sequencing
  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 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.4.1 Integer N Divide Portion (PLL_N)

Due to the requirements of the total N divider value to handle fractions and also high frequency, there are limitations based the modulator order and VCO frequency.

When using the internal VCO, the true minimum N divide is based on the VCO core. The VCO core frequencies may shift some with process, so the most reasonable thing to do is based this on worst case assumption for the VCO Core.

Table 7-2 Minimum N Divider Value for Internal VCO
fVCO WORST CASE CORE MASH_ORDER = 0 MASH_ORDER = 1 MASH_ORDER = 2 MASH_ORDER = 3
5.65 - 6.35 GHz VCO1 12 18 19 24
6.35 - 7.3 GHz VCO2 14 21 22 26
7.3 - 8.1 GHz VCO3 16 23 24 26
8.1 - 9.0 GHz VCO4 16 26 27 29
9.0 - 9.8 GHz VCO5 18 28 29 31
9.8 - 10.6 GHz VCO6 18 30 31 33
10.6 - 11.3 GHz VCO7 20 33 34 36

For the external VCO, the minimum N divides are slightly different. In cases where the VCO frequency is higher than 11.3 GHz, the VCO frequency must divided by 2 by setting EXTVCO_DIV bit.

Table 7-3 Minimum N Divider for External VCO
fRFIN / (RFIN Divider)MASH_ORDER = 0MASH_ORDER = 1MASH_ORDER = 2MASH_ORDER = 3
0.5 - 4 GHz12121420
4 - 5.5 GHz12151824
5.5 - 7 GHz14182026
7 - 8.5 GHz16232426
8.5 - 10 GHz20282935
10 GHz - 11.3 GHz20323335