SNOSCP7A March   2013  – January 2016 LMX2485Q-Q1

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 - Commercial
    3. 6.3 ESD Ratings - Automotive
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Information
    6. 6.6 Electrical Characteristics
    7. 6.7 Timing Characteristics
    8. 6.8 Typical Characteristics
      1. 6.8.1 Sensitivity
      2. 6.8.2 FinRF Input Impedance
      3. 6.8.3 FinIF Input Impedance
      4. 6.8.4 OSCin Input Impedance
      5. 6.8.5 Currents
  7. 7 Parameter Measurement Information
    1. 7.1 Bench Test Set-Ups
      1. 7.1.1 Charge Pump Current Measurement Procedure
      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 Sink Current vs Charge Pump Output Source Current Mismatch
        3. 7.1.2.3 Charge Pump Output Current Variation vs Temperature
      3. 7.1.3 Sensitivity Measurement Procedure
      4. 7.1.4 Input Impedance Measurement Procedure
  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 Register Location Truth Table
      2. 8.5.2 Control Register Content Map
    6. 8.6 Register Maps
      1. 8.6.1 R0 Register
      2. 8.6.2 R1 Register
      3. 8.6.3 R2 Register
      4. 8.6.4 R3 Register
      5. 8.6.5 R4 Register
      6. 8.6.6 R5 Register
      7. 8.6.7 R6 Register
      8. 8.6.8 R7 Register
  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

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RTW|24
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

This device ideal for use in a broad class of applications, especially those requiring low current consumption and low fractional spurs. For applications that only need a single PLL, the unused PLL can be powered down and will not draw any extra current or generate any spurs or crosstalk. The automotive qualification on this device makes it ideal for automotive applications.

9.2 Typical Application

LMX2485Q-Q1 sch_apps_snoscp7.gif Figure 33. Typical Application With Only One Side Used

9.2.1 Design Requirements

Table 44 lists the design parameters of the LMX2485Q-Q1.

Table 44. Design Parameters

PARAMETER VALUE
PM Phase Margin 48.3 degrees
BW Loop Bandwidth 11.3 KHz
T3/T1 Pole Ratio 40.20%
T4/T3 36.30%
KPD Charge Pump Gain 400 µA
fPD Phase Detector Frequncy 10 MHz
fVCO VCO Frequency 2400 – 2480 MHz
Vcc Supply Voltage 3 V
KVCO VCO Gain 55 MHz/V
CVCO VCO Input Capacitance 22 pF
C1_LF Loop Filter Components 2.7 nF
C2_LF 47 nF
C3_LF 270 pF
C4_LF 180 pF
R2_LF 820 Ω
R3_LF 3.9 kΩ
R4_LF 5.6 kΩ

9.2.2 Detailed Design Procedure

The design of the loop filter involves balancing requirements of lock time, spurs, and phase noise. This design is fairly involved, but the TI website has references, design tools, and simulation tools cover the loop filter design and simulation in depth.

9.2.3 Application Curves

LMX2485Q-Q1 ta_phasenoise_snoscp7.png
Figure 34. Phase Noise
LMX2485Q-Q1 ta_spur_snoscp7.png
Figure 35. Fractional Spur for 200-kHz Channel Spacing