Automotive Delta-Sigma Low Power Dual PLL for RF Personal Communications - LMX2485Q-Q1


Automotive Delta-Sigma Low Power Dual PLL for RF Personal Communications


Recommended alternative parts

  • LMX2485  -  3.0 GHz Maximum Operating Frequency


The LMX2485Q-Q1 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 LMX2485Q-Q1 is highly resistant to changes in temperature and variations in wafer processing. The LMX2485Q-Q1 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 LMX2485Q-Q1 is transferred through a three-line, high-speed (20-MHz) MICROWIRE interface. The LMX2485Q-Q1 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 LMX2485Q-Q1 is available in a 24-lead 4.0 × 4.0 × 0.8 mm WQFN package.


  • Quadruple Modulus Prescaler for Lower Divides
    • RF PLL: 8/9/12/13 or 16/17/20/21
    • 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
  • Improved Lock Times and Programming
    • Fastlock / Cycle Slip Reduction Requiring Only
      a Single-Word Write
    • Integrated Time-Out Counter
  • Wide Operating Range
    • LMX2485Q-Q1 RF PLL: 500 MHz to 3.1 GHz
  • Useful Features
    • Digital Lock Detect Output
    • Hardware and Software Power-Down Control
    • On-Chip Input Frequency Doubler
    • RF Phase Detector Frequency Up to 50 MHz
    • 2.5-V to 3.6-V Operation With ICC = 5.0 mA
    • LMX2485Q-Q1 is AEC-Q100 Grade 2
      Qualified and is Manufactured on an
      Automotive Grade Flow

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Parametrics Compare all products in RF PLLs and Synthesizers

Output Frequency (Min) (MHz)
Output Frequency (Max) (MHz)
Normalized PLL Phase Noise (dBc/Hz)
1/f Noise (10 kHz offset at 1 GHz carrier) (dBc/Hz)
Current Consumption (mA)
Integrated VCO
LMX2485Q-Q1 LMX2485E LMX2486 LMX2487 LMX2487E LMX2492-Q1
500    50    1000    1000    3000    500   
3100    3000    4500    6000    7500    14000   
-210    -210    -210    -210    -210    -227   
-104    -104    -104    -104    -104    -120   
3.3    3.3    5.7    5.7    5.7    60   
2.5 to 3.6    2.5 to 3.6    2.5 to 3.6    2.5 to 3.6    2.5 to 3.6    3.15 to 3.45   
No    No    No    No    No    No   
24WQFN    24WQFN    24WQFN    24WQFN    24WQFN    24WQFN   

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