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

8.1.3 Using Instant Calibration

Instant calibration allows the device to very quickly calibrate the VCO in 2.5 µs and choose the same calibration settings (rb_VCO_SEL, rb_VCO_DACISET, rb_VCO_CAPCTRL). Once this feature is initialized, then there is no overhead in changing the VCO frequency. This initialization is required when the device is initially powered up, but the settings are retained, provided power is not removed from the supply pins. The following procedure details how this is done:

  1. Power up device Normally.
  2. Program INSTCAL_DLY = tDLY × fOSC (in MHz)/ 2CAL_CLK_DIV. tDLY is the required timeout count for instant calibration and is based on the bias capacitor at pin 3.
    Table 8-2 Determining Instant Calibration Timeout
    PIN 3 CAPACITANCE PLL 1/f NOISE DEGRADATION MINIMUM tDLY
    0.47 μF 1 dB 2.5 μs
    C 0-1 dB 2.5 μs × C/(0.47 μF)
    4.7 μF 0 dB 25 μs
  3. Program register R1 for Instant Calibration.
    • Set INSTCAL_EN = 1. The action of toggling INSTCAL_EN from 0 to 1 resets the instant calibration settings and sets the part up to generate settings the next time that register R0 is programmed with FCAL_EN = 1.
    • If the output doubler is used set INSTCAL_DBLR_EN = 1, otherwise set it to 0
  4. Program the device to output 5.65 GHz.
  5. Program INSTCAL_PLL_NUM = 232 × (PLL_NUM / PLL_DEN).
  6. Write R0 with FCAL_EN = 1 to generate the calibration settings.
  7. Write R0 with FCAL_EN = 0 to have the device lock to 5.65 GHz
  8. Wait for Lock Detect to go high.

Now the device is initialized for the particular phase detector frequency that this was done at. Provided that power is not removed from the device and then phase detector frequency does not change, subsequent frequency changes an be done using the instant cal. To change frequencies after the instant calibration is initialized:

  1. Write the values for INSTCAL_PLL_NUM, PLL_N, PLL_NUM, PLL_DEN.
  2. Write R0 to trigger Calibration (with DBLR_CAL_EN = 0, FCAL_EN = 0).