SNOSB31J July   2009  – December 2014 LMX2541

PRODUCTION DATA.  

  1. 1 Features
  2. 2  Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
      1. 7.7.1 Not Ensured Characteristics
      2. 7.7.2 Output Power in Bypass Mode
      3. 7.7.3 Output Power in Divided Mode
      4. 7.7.4 RFout Output Impedance
        1. 7.7.4.1 OSCin and Fin Sensitivity
  8. 8 Parameter Measurement Information
    1. 8.1 Bench Test Setups
      1. 8.1.1 Charge Pump Current Measurements
      2. 8.1.2 Charge Pump Current Definitions
        1. 8.1.2.1 Charge Pump Current Definitions
        2. 8.1.2.2 Variation of Charge Pump Current Magnitude vs. Charge Pump Voltage
        3. 8.1.2.3 Variation of Charge Pump Current Magnitude vs. Temperature
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagrams
    3. 9.3 Feature Description
      1. 9.3.1  PLL Reference Oscillator Input Pins
      2. 9.3.2  PLL R Divider
      3. 9.3.3  PLL Phase Detector and Charge Pump
      4. 9.3.4  PLL N Divider and Fractional Circuitry
      5. 9.3.5  Partially Integrated Loop Filter
      6. 9.3.6  Low Noise, Fully Integrated VCO
      7. 9.3.7  Programmable VCO Divider
      8. 9.3.8  Programmable RF Output Buffer
      9. 9.3.9  Powerdown Modes
      10. 9.3.10 Fastlock
      11. 9.3.11 Lock Detect
      12. 9.3.12 Current Consumption
      13. 9.3.13 Fractional Spurs
        1. 9.3.13.1 Primary Fractional Spurs
        2. 9.3.13.2 Sub-Fractional Spurs
      14. 9.3.14 Impact of VCO_DIV on Fractional Spurs
      15. 9.3.15 PLL Phase Noise
        1. 9.3.15.1 , LMX2541SQ3740E Raw Phase Noise Measurement Plot Description
        2. 9.3.15.2 , LMX2541SQ2690 System Phase Noise Plot Description
        3. 9.3.15.3 Phase Noise of PLL
      16. 9.3.16 Impact of Modulator Order, Dithering, and Larger Equivalent Fractions on Spurs and Phase Noise
      17. 9.3.17 Modulator Order
      18. 9.3.18 Programmable Output Power with On/Off
      19. 9.3.19 Loop Filter
      20. 9.3.20 Internal VCO Digital Calibration Time
    4. 9.4 Device Functional Modes
      1. 9.4.1 External VCO Mode
      2. 9.4.2 Digital FSK Mode
    5. 9.5 Programming
      1. 9.5.1 General Programming Information
    6. 9.6 Register Maps
      1. 9.6.1 Register R7
        1. 9.6.1.1  Register R13
          1. 9.6.1.1.1 VCO_DIV_OPT[2:0]
        2. 9.6.1.2  Register R12
        3. 9.6.1.3  Register R9
        4. 9.6.1.4  Register R8
          1. 9.6.1.4.1 AC_TEMP_COMP[4:0]
        5. 9.6.1.5  Register R6
          1. 9.6.1.5.1 RFOUT[1:0] - RFout enable pin
          2. 9.6.1.5.2 DIVGAIN[3:0], VCOGAIN[3:0], and OUTTERM[3:0] - Power Controls for RFout
        6. 9.6.1.6  Register R5
          1. 9.6.1.6.1 FL_TOC[13:0] -- Time Out Counter for FastLock
          2. 9.6.1.6.2 FL_R3_LF[2:0] -- Value for Internal Loop Filter Resistor R3 During Fastlock
          3. 9.6.1.6.3 FL_R4_LF[2:0] -- Value for Internal Loop Filter Resistor R4 During Fastlock
          4. 9.6.1.6.4 FL_CPG[4:0] -- Charge Pump Current for Fastlock
        7. 9.6.1.7  Register R4
          1. 9.6.1.7.1 OSC_FREQ [7:0] -- OSCin Frequency for VCO Calibration Clocking
          2. 9.6.1.7.2 VCO_DIV[5:0] - VCO Divider
          3. 9.6.1.7.3 R3_LF[2:0] -- Value for Internal Loop Filter Resistor R3
          4. 9.6.1.7.4 R4_LF[2:0] -- Value for Internal Loop Filter Resistor R4
          5. 9.6.1.7.5 C3_LF[3:0] -- Value for C3 in the Internal Loop Filter
          6. 9.6.1.7.6 C4_LF[3:0] -- Value for C4 in the Internal Loop Filter
        8. 9.6.1.8  Register R3
          1. 9.6.1.8.1  MODE[1:0] -- Operational Mode
          2. 9.6.1.8.2  Powerdown -- Powerdown Bit
          3. 9.6.1.8.3  XO - Crystal Oscillator Mode Select
          4. 9.6.1.8.4  CPG[4:0] -- Charge Pump Current
          5. 9.6.1.8.5  MUX[3:0] -- Multiplexed Output for Ftest/LD Pin
          6. 9.6.1.8.6  CPP - Charge Pump Polarity
          7. 9.6.1.8.7  OSC2X-- OSCin Frequency Doubler
          8. 9.6.1.8.8  FDM - Extended Fractional Denominator Mode Enable
          9. 9.6.1.8.9  ORDER[2:0] -- Delta-Sigma Modulator Order
          10. 9.6.1.8.10 DITH[1:0] -- Dithering
          11. 9.6.1.8.11 CPT - Charge Pump TRI-STATE
          12. 9.6.1.8.12 DLOCK[2:0] - Controls for Digital Lock Detect
          13. 9.6.1.8.13 FSK - Frequency Shift Keying
        9. 9.6.1.9  Register R2
          1. 9.6.1.9.1 PLL_DEN[21:0] -- Fractional Denominator
        10. 9.6.1.10 Registers R1 and R0
          1. 9.6.1.10.1 PLL_R[11:0] -- PLL R Divider Value
          2. 9.6.1.10.2 PLL_N[17:0] PLL N Divider Value
          3. 9.6.1.10.3 PLL_NUM[21:0] -- Fractional Numerator
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Determining the Best Frequency Option of the LMX2541 to Use
      2. 10.1.2 RFout Output Power Test Setup
      3. 10.1.3 Phase Noise Measurement Test Setup
        1. 10.1.3.1 PLL Phase Noise Measurement
          1. 10.1.3.1.1 PLL Phase Noise Measurement - 1/f Noise
          2. 10.1.3.1.2 PLL Phase Noise Measurement - Flat Noise
        2. 10.1.3.2 VCO Phase Noise Measurement
        3. 10.1.3.3 Divider Phase Noise Measurement
      4. 10.1.4 Input and Output Impedance Test Setup
        1. 10.1.4.1 OSCin Input Impedance Measurement
        2. 10.1.4.2 ExtVCOin Input Impedance Measurement
        3. 10.1.4.3 RFout Output Impedance Measurement
      5. 10.1.5 ExtVCOin (NOT OSCin) Input Sensitivity Test Setup
      6. 10.1.6 OSCin Input Sensitivity Test Setup
        1. 10.1.6.1 Input Sensitivity Test Procedure
        2. 10.1.6.2 OSCin Slew Rate Tests
      7. 10.1.7 Typical Connections
        1. 10.1.7.1 Full Chip Mode, Differential OSCin
        2. 10.1.7.2 External VCO Mode, Single-Ended OSCin, RFout Pin not Used
        3. 10.1.7.3 OSCin/OSCin* Connections
          1. 10.1.7.3.1 Single-Ended Operation
          2. 10.1.7.3.2 Differential Operation
          3. 10.1.7.3.3 Crystal Mode Operation
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Configuring the LMX2541 for Optimal Performance
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
    2. 13.2 Trademarks
    3. 13.3 Electrostatic Discharge Caution
    4. 13.4 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • NJK|36
Thermal pad, mechanical data (Package|Pins)
Orderable Information

1 Features

  • Multiple Frequency Options Available
    (See Device Comparison Table)
  • Frequencies From 31.6 MHz to 4000 MHz
  • Very Low RMS Noise and Spurs
  • –225 dBc/Hz Normalized PLL Phase Noise
  • Integrated RMS Noise (100 Hz to 20 MHz)
    • 2 mRad (100 Hz to 20 MHz) at 2.1 GHz
    • 3.5 mRad (100 Hz to 20 MHz) at 3.5 GHz
  • Ultra Low-Noise Integrated VCO
  • External VCO Option (Internal VCO Bypassed)
  • VCO Frequency Divider 1 to 63 (All Values)
  • Programmable Output Power
  • Up to 104-MHz Phase Detector Frequency
  • Integrated Low-Noise LDOs
  • Programmable Charge Pump Output
  • Partially Integrated Loop Filter
  • Digital Frequency Shift Keying (FSK) Modulation Pin
  • Integrated Reference Crystal Oscillator Circuit
  • Hardware and Software Power Down
  • FastLock Mode and VCO-Based Cycle Slip Reduction
  • Analog and Digital Lock Detect
  • 1.6-V Logic Compatibility

2 Applications

  • Wireless Infrastructure (UMTS, LTE, WiMax)
  • Broadband Wireless
  • Wireless Meter Reading
  • Test and Measurement
  • FM Mobile Radio

3 Description

The LMX2541 device is an ultra low-noise frequency synthesizer which integrates a high-performance delta-sigma fractional N PLL, a VCO with fully integrated tank circuit, and an optional frequency divider. The PLL offers an unprecedented normalized noise floor of –225 dBc/Hz and can be operated with up to 104 MHz of phase-detector rate (comparison frequency) in both integer and fractional modes. The PLL can also be configured to work with an external VCO.

The LMX2541 integrates several low-noise, high-precision LDOs and output driver matching network to provide higher supply noise immunity and more consistent performance, while reducing the number of external components. When combined with a high-quality reference oscillator, the LMX2541 generates a very stable, ultra low-noise signal.

The LMX2541 is offered in a family of 6 devices with varying VCO frequency range from 1990 MHz up to 4 GHz. Using a flexible divider, the LMX2541 can generate frequencies as low as 31.6 MHz.

The LMX2541 is a monolithic integrated circuit, fabricated in a proprietary BiCMOS process. Device programming is facilitated using a three-wire MICROWIRE interface that can operate down to 1.6 volts. Supply voltage ranges from 3.15 V to 3.45 V. The LMX2541 is available in a 36-pin 6-mm × 6-mm × 0.8-mm WQFN package.

Device Information(1)

PART NUMBER PACKAGE VCO FREQUENCY (MHz)
LMX2541SQ2060E WQFN (36) 1990 - 2240
LMX2541SQ2380E WQFN (36) 2200 - 2530
LMX2541SQ2690E WQFN (36) 2490 - 2865
LMX2541SQ3030E WQFN (36) 2810 - 3230
LMX2541SQ3320E WQFN (36) 3130 - 3600
LMX2541SQ3740E WQFN (36) 3480 - 4000
  1. For all available packages, see the orderable addendum at the end of the data sheet.

System Block Diagram

LMX2541 30073322.gif