SNAS324B January   2006  – January 2016 LMX2486

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
      1. 6.7.1 Sensitivity
      2. 6.7.2 FinRF Input Impedance
      3. 6.7.3 FinIF Input Impedance
      4. 6.7.4 OSCin Input Impedance
      5. 6.7.5 Currents
  7. 7 Parameter Measurements Information
    1. 7.1 Bench Test Set-Ups
      1. 7.1.1 Charge Pump Current Measurement
      2. 7.1.2 Charge Pump Current Specification Definitions
        1. 7.1.2.1 Charge Pump Output Current Variation vs Charge Pump Output Voltage
        2. 7.1.2.2 Charge Pump Output Current Variation vs Temperature
      3. 7.1.3 Sensitivity Measurement
      4. 7.1.4 Input Impedance Measurement
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 TCXO, Oscillator Buffer, and R Counter
      2. 8.3.2 Phase Detector
      3. 8.3.3 Charge Pump
      4. 8.3.4 Loop Filter
      5. 8.3.5 N Counters and High Frequency Input Pins
        1. 8.3.5.1 High Frequency Input Pins, FinRF and FinIF
        2. 8.3.5.2 Complementary High Frequency Pin, FinRF*
      6. 8.3.6 Digital Lock Detect Operation
      7. 8.3.7 Cycle Slip Reduction and Fastlock
        1. 8.3.7.1 Cycle Slip Reduction (CSR)
        2. 8.3.7.2 Fastlock
        3. 8.3.7.3 Using Cycle Slip Reduction (CSR) to Avoid Cycle Slipping
        4. 8.3.7.4 Using Fastlock to Improve Lock Times
        5. 8.3.7.5 Capacitor Dielectric Considerations for Lock Time
      8. 8.3.8 Fractional Spur and Phase Noise Controls
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power Pins, Power-Down, and Power-Up Modes
    5. 8.5 Programming
      1. 8.5.1 General Programming Information
        1. 8.5.1.1 Register Location Truth Table
        2. 8.5.1.2 Control Register Content Map
    6. 8.6 Register Maps
      1. 8.6.1 R0 Register
        1. 8.6.1.1 RF_FN[11:0] -- Fractional Numerator for RF PLL
        2. 8.6.1.2 RF_N[10:0] -- RF N Counter Value
      2. 8.6.2 R1 Register
        1. 8.6.2.1 RF_FD[11:0] -- RF PLL Fractional Denominator
        2. 8.6.2.2 RF_R [5:0] -- RF R Divider Value
        3. 8.6.2.3 RF_P -- RF Prescaler bit
        4. 8.6.2.4 RF_PD -- RF Power Down Control Bit
      3. 8.6.3 R2 Register
        1. 8.6.3.1 IF_N[18:0] -- IF N Divider Value
        2. 8.6.3.2 IF_PD -- IF Power Down Bit
      4. 8.6.4 R3 Register
        1. 8.6.4.1 IF_R[11:0] -- IF R Divider Value
        2. 8.6.4.2 RF_CPG -- RF PLL Charge Pump Gain
        3. 8.6.4.3 Access -- Register Access Word
      5. 8.6.5 R4 Register
        1. 8.6.5.1 MUX[3:0] Frequency Out and Lock Detect MUX
        2. 8.6.5.2 IF_P -- IF Prescaler
        3. 8.6.5.3 RF_CPP -- RF PLL Charge Pump Polarity
        4. 8.6.5.4 IF_CPP -- IF PLL Charge Pump Polarity
        5. 8.6.5.5 OSC_OUT Oscillator Output Buffer Enable
        6. 8.6.5.6 OSC2X -- Oscillator Doubler Enable
        7. 8.6.5.7 FM[1:0] -- Fractional Mode
        8. 8.6.5.8 DITH[1:0] -- Dithering Control
        9. 8.6.5.9 ATPU -- PLL Automatic Power Up
      6. 8.6.6 R5 Register
        1. 8.6.6.1 Fractional Numerator Determination { RF_FN[21:12], RF_FN[11:0], Access[1] }
        2. 8.6.6.2 Fractional Denominator Determination { RF_FD[21:12], RF_FD[11:0], Access[1]}
      7. 8.6.7 R6 Register
        1. 8.6.7.1 RF_TOC -- RF Time-Out Counter and Control for FLoutRF Pin
        2. 8.6.7.2 RF_CPF -- RF PLL Fastlock Charge Pump Current
        3. 8.6.7.3 CSR[1:0] -- RF Cycle Slip Reduction
      8. 8.6.8 R7 Register
        1. 8.6.8.1 DIV4 -- RF Digital Lock Detect Divide By 4
        2. 8.6.8.2 IF_RST -- IF PLL Counter Reset
        3. 8.6.8.3 RF_RST -- RF PLL Counter Reset
        4. 8.6.8.4 RF_TRI -- RF Charge Pump TRI-STATE
        5. 8.6.8.5 IF_TRI -- IF Charge Pump TRI-STATE
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Community Resources
    2. 12.2 Trademarks
    3. 12.3 Electrostatic Discharge Caution
    4. 12.4 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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订购信息

1 Features

  • Quadruple Modulus Prescaler for Lower Divids
    • RF PLL: 16/17/20/21 or 32/33/36/37
    • IF PLL: 8/9 or 16/17
  • Advanced Delta Sigma Fractional Compensation
    • 12-Bit or 22-Bit Selectable Fractional Modulus
    • Up to 4th Order Programmable Delta-Sigma Modulator
  • Improved Lock Times and Programming
    • Fastlock / Cycle Slip Reduction Which Requires Only a Single-Word Write
    • Integrated Time-Out Counter
  • Wide Operating Range
    • LMX2486 RF PLL: 1.0 GHz to 4.5 GHz
  • Useful Features
    • Digital Lock Detect Output
    • Hardware and Software Power-Down Control
    • On-Chip Crystal Reference Frequency Doubler
    • RF Phase Detector Frequency Up to 50 MHz
    • 2.5-V to 3.6-V Operation With ICC = 8.5 mA

2 Applications

  • Cellular Phones and Base Stations
  • Direct Digital Modulation Applications
  • Satellite and Cable TV Tuners
  • WLAN Standards

3 Description

The LMX2486 device is a low-power, high performance delta-sigma fractional-N PLL with an auxiliary integer-N PLL. The device is fabricated using TI’s advanced process.

With delta-sigma architecture, fractional spurs at lower offset frequencies are pushed to higher frequencies outside the loop bandwidth. The ability to push close in spur and phase noise energy to higher frequencies is a direct function of the modulator order. Unlike analog compensation, the digital feedback technique used in the LMX2486 is highly resistant to changes in temperature and variations in wafer processing. The LMX2486 delta-sigma modulator is programmable up to fourth order, which allows the designer to select the optimum modulator order to fit the phase noise, spur, and lock time requirements of the system.

Serial data for programming the LMX2486 is transferred through a three-line, high-speed (20-MHz) MICROWIRE interface. The LMX2486 offers fine frequency resolution, low spurs, fast programming speed, and a single-word write to change the frequency. This makes it ideal for direct digital modulation applications, where the N-counter is directly modulated with information. The LMX2486 is available in a 24-lead 4.0 × 4.0 × 0.8 mm WQFN package.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LMX2486 WQFN (24) 4.00 mm × 4.00 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Functional Block Diagram

LMX2486 20154701.gif