SNAS601G August   2012  – September 2014 LMX2581

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematic
  5. 5 Revision History
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Handling Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements, MICROWIRE Timing
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Typical Performance Characteristics
        1. 8.3.1.1 Phase Noise Typical Performance Plot Explanations
        2. 8.3.1.2 Other Typical Performance Plot Characteristics Explanations
      2. 8.3.2  Impact of Temperature on VCO Phase Noise
      3. 8.3.3  OSCin INPUT and OSCin Doubler
      4. 8.3.4  R Divider
      5. 8.3.5  PLL N Divider And Fractional Circuitry
        1. 8.3.5.1 Programmable Dithering Levels
        2. 8.3.5.2 Programmable Delta Sigma Modulator Order
      6. 8.3.6  PLL Phase Detector and Charge Pump
      7. 8.3.7  External Loop Filter
      8. 8.3.8  Low Noise, Fully Integrated VCO
        1. 8.3.8.1 VCO Digital Calibration
      9. 8.3.9  Programmable VCO Divider
      10. 8.3.10 0-Delay Mode
      11. 8.3.11 Programmable RF Output Buffers
        1. 8.3.11.1 Choosing the Proper Pull-Up Component
        2. 8.3.11.2 Choosing the Best Setting for the RFoutA_PWR and RFoutB_PWR Words
      12. 8.3.12 Fastlock
      13. 8.3.13 Lock Detect
        1. 8.3.13.1 Vtune Lock Detect
        2. 8.3.13.2 Digital Lock Detect (DLD)
      14. 8.3.14 Part ID and Register Readback
        1. 8.3.14.1 Uses of Readback
        2. 8.3.14.2 Serial Timing for Readback
      15. 8.3.15 Optimization of Spurs
        1. 8.3.15.1 Phase Detector Spur
        2. 8.3.15.2 Fractional Spur - Integer Boundary Spur
        3. 8.3.15.3 Fractional Spur - Primary Fractional Spurs
        4. 8.3.15.4 Fractional Spur - Sub-Fractional Spurs
        5. 8.3.15.5 Summary of Spurs and Mitigation Techniques
    4. 8.4 Device Functional Modes
      1. 8.4.1 Full Synthesizer Mode
      2. 8.4.2 External VCO Mode
      3. 8.4.3 Powerdown Modes
    5. 8.5 Programming
      1. 8.5.1 Serial Data Input Timing
      2. 8.5.2 Recommended Initial Power on Programming Sequence
      3. 8.5.3 Recommended Sequence for Changing Frequencies
      4. 8.5.4 Triggering Registers
    6. 8.6 Register Maps
      1. 8.6.1 Programming Word Descriptions
        1. 8.6.1.1  Register R15
          1. 8.6.1.1.1 VCO_CAP_MAN — Manual VCO Band Select
          2. 8.6.1.1.2 VCO_CAPCODE[7:0] — Capacitor Value for VCO Band Selection
        2. 8.6.1.2  Register R13
          1. 8.6.1.2.1 DLD_ERR_CNT[3:0] - Digital Lock Detect Error Count
          2. 8.6.1.2.2 DLD_PASS_CNT[9:0] - Digital Lock Detect Success Count
          3. 8.6.1.2.3 DLD_TOL[2:0] — Digital Lock Detect
        3. 8.6.1.3  Registers R10, R9, and R8
        4. 8.6.1.4  Register R7
          1. 8.6.1.4.1 FL_PINMODE[2:0], MUXOUT_PINMODE[2:0], and LD_PINMODE[2:0] — Output Format for Status Pins
          2. 8.6.1.4.2 FL_INV, MUX_INV, LD_INV - Inversion for Status Pins
          3. 8.6.1.4.3 FL_SELECT[4:0], MUXOUT_SELECT[4:0], LD_SELECT[4:0] — State for Status Pins
        5. 8.6.1.5  Register R6
          1. 8.6.1.5.1 RD_DIAGNOSTICS[19:0] — Readback Diagnostics
          2. 8.6.1.5.2 RDADDR[3:0] — Readback Address
          3. 8.6.1.5.3 uWIRE_LOCK - Microwire lock
        6. 8.6.1.6  Register R5
          1. 8.6.1.6.1  OUT_LDEN — Mute Outputs Based on Lock Detect
          2. 8.6.1.6.2  OSC_FREQ[2:0] — OSCin Frequency for VCO Calibration
          3. 8.6.1.6.3  BUFEN_DIS - Disable for the BUFEN Pin
          4. 8.6.1.6.4  VCO_SEL_MODE — Method of Selecting Internal VCO Core
          5. 8.6.1.6.5  OUTB_MUX — Mux for RFoutB
          6. 8.6.1.6.6  OUTA_MUX — Mux for RFoutA
          7. 8.6.1.6.7  0_DLY - Zero Delay Mode
          8. 8.6.1.6.8  MODE[1:0] — Operating Mode
          9. 8.6.1.6.9  PWDN_MODE - Powerdown Mode
          10. 8.6.1.6.10 RESET - Register Reset
        7. 8.6.1.7  Register R4
          1. 8.6.1.7.1 PFD_DLY[2:0] — Phase Detector Delay
          2. 8.6.1.7.2 FL_FRCE — Force Fastlock Conditions
          3. 8.6.1.7.3 FL_TOC[11:0] — Fastlock Timeout Counter
          4. 8.6.1.7.4 FL_CPG[4:0] — Fastlock Charge Pump Gain
          5. 8.6.1.7.5 CPG_BLEED[5:0]
        8. 8.6.1.8  Register R3
          1. 8.6.1.8.1 VCO_DIV[4:0] — VCO Divider Value
          2. 8.6.1.8.2 OUTB_PWR[5:0] — RFoutB Output Power
          3. 8.6.1.8.3 OUTA_PWR[5:0] — RFoutA Output Power
          4. 8.6.1.8.4 OUTB_PD — RFoutB Powerdown
          5. 8.6.1.8.5 OUTA_PD — RFoutA Powerdown
        9. 8.6.1.9  Register R2
          1. 8.6.1.9.1 OSC_2X — OSCin Doubler
          2. 8.6.1.9.2 CPP - Charge Pump Polarity
          3. 8.6.1.9.3 PLL_DEN[21:0] — PLL Fractional Denominator
        10. 8.6.1.10 Register R1
          1. 8.6.1.10.1 CPG[4:0] — PLL Charge Pump Gain
          2. 8.6.1.10.2 VCO_SEL[1:0] - VCO Selection
          3. 8.6.1.10.3 FRAC_ORDER[2:0] — PLL Delta Sigma Modulator Order
          4. 8.6.1.10.4 PLL_R[7:0] — PLL R divider
        11. 8.6.1.11 Register R0
          1. 8.6.1.11.1 ID - Part ID Readback
          2. 8.6.1.11.2 FRAC_DITHER[1:0] — PLL Fractional Dithering
          3. 8.6.1.11.3 NO_FCAL — Disable Frequency Calibration
          4. 8.6.1.11.4 PLL_N - PLL Feedback Divider Value
          5. 8.6.1.11.5 PLL_NUM[21:12] and PLL_NUM[11:0] — PLL Fractional Numerator
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Clocking Application
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Fractional PLL Application
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
    3. 9.3 Do's and Don'ts
  10. 10Power Supply Recommendations
    1. 10.1 Supply Recommendations
    2. 10.2 Regulator Output Pins
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

1 Features

  • Output Frequency from 50 to 3760 MHz
  • Input Clock Frequency up to 900 MHz
  • Phase Detector Frequency up to 200 MHz
  • Supports Fractional and Integer Modes
  • –229 dBc/Hz Normalized PLL Phase Noise
  • –120.8 dBc/Hz Normalized PLL 1/f Noise
  • –137 dBc/Hz VCO Phase Noise @ 1 MHz offset for a 2.5 GHz Carrier
  • 100 fs RMS Jitter in Integer Mode
  • Programmable Fractional Modulator Order
  • Programmable Fractional Denominator
  • Programmable Output Power up to +12 dBm
  • Programmable 32 Level Charge Pump Current
  • Programmable Option to Use an External VCO
  • Digital Lock Detect
  • 3-Wire Serial Interface and Readback
  • Single Supply Voltage from 3.15 V to 3.45 V
  • Supports Logic Levels down to 1.6 V

2 Applications

  • Wireless Infrastructure (UMTS, LTE, WiMax, Multi-Standard Base Stations)
  • Broadband Wireless
  • Test and Measurement
  • Clock Generation

3 Description

The LMX2581 is a low noise wideband frequency synthesizer that integrates a delta-sigma fractional N PLL, multiple core VCO, programmable output divider, and two differential output buffers. The VCO frequency range is from 1880 to 3760 MHz and can be sent directly to the output buffers or divided down by even values from 2 to 38. Each buffer is capable of output power from -3 to +12 dBm at 2700 MHz. Integrated low noise LDOs are used for superior noise immunity and consistent performance.

This synthesizer is a highly programmable device and it enables the user to optimize its performance. In fractional mode, the denominator and the modulator order are programmable and can be configured with dithering as well. The user also has the ability to directly specify a VCO core or entirely bypass the internal VCO. Finally, many convenient features are included such as power down, Fastlock, auto mute, and lock detection. All registers can be programmed through a simple 3 wire interface and a read back feature is also available.

The LMX2581 operates on a single 3.3 V supply and comes in a 32 pin 5.0 mm × 5.0 mm WQFN package.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LMX2581 WQFN (32) 5.00 mm × 5.00 mm
  1. For all available packages, see the orderable addendum at the end of the datasheet.

4 Simplified Schematic

sch_front_snas601.gif