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

7.4.1 External VCO Mode

An external VCO can also be used with the LMX2820, but note that the output buffers cannot be used while the SYSREF feature can. The charge pump voltage maximum output voltage is about 2.5 V, but this is not sufficient for most VCOs. For this reason, an active filter is recommended, which can keep the charge pump voltage biased around 1.2 V and provide the higher output voltage. If the VCO frequency is higher than 11.3 GHz, the EXTVCODIV bit must be enabled, otherwise, it should be zero.

GUID-20200811-CA0I-GCVZ-G2MF-ZTKCPJMQ9ZH5-low.gif Figure 7-6 External VCO Mode

When using the external VCO, the PFD_DLY word must be set manually as shown in Table 7-9. For the case of an integrated VCO, it is not necessary to program this word. PFD_DLY_MANUAL = 1 is required to manually set the PFD_DLY.

Table 7-9 PFD_DLY_SEL Settings for External VCO Mode
fRFIN/(RFIN Divider) MASH_ORDER = 0 MASH_ORDER = 1 MASH_ORDER = 2 MASH_ORDER = 3
0.5 - 4 GHz 1 1 2 4
4 - 5.5 GHz 2 2 3 5
5.5 - 7 GHz 3 3 4 6
7 - 8.5 GHz 4 4 5 7
8.5 - 10 GHz 5 5 6 8
> 10 GHz 6 6 7 9