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LMX2485E

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50-MHz to 3-GHz delta-sigma low power dual PLL for RF personal communications

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Data sheet

LMX2485E

ACTIVE
Data sheet Order now

Product details

Integrated VCO No Output frequency (min) (MHz) 50 Output frequency (max) (MHz) 3000 Normalized PLL phase noise (dBc/Hz) -210 Current consumption (mA) 3.3 Features Advanced delta-sigma fractional compensation, Cycle slip reduction, Dual PLL, Fastlock, Integrated timeout counter, On-chip input frequency doubler 1/f noise (10-kHz offset at 1-GHz carrier) (dBc/Hz) -104 Rating Catalog Operating temperature range (°C) -40 to 85 Lock time (µs) (typ) Loop BW dependent
Integrated VCO No Output frequency (min) (MHz) 50 Output frequency (max) (MHz) 3000 Normalized PLL phase noise (dBc/Hz) -210 Current consumption (mA) 3.3 Features Advanced delta-sigma fractional compensation, Cycle slip reduction, Dual PLL, Fastlock, Integrated timeout counter, On-chip input frequency doubler 1/f noise (10-kHz offset at 1-GHz carrier) (dBc/Hz) -104 Rating Catalog Operating temperature range (°C) -40 to 85 Lock time (µs) (typ) Loop BW dependent
WQFN (RTW) 24 16 mm² 4 x 4
  • 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
      Modulator
  • Features for Improved Lock Time
    • Fastlock / Cycle Slip Reduction With Integrated
      Time-Out Counter Which Requires Only a
      Single-Word Write
  • Wide Operating Range
    • LMX2485 RF PLL: 500 MHz to 3.0 GHz
    • LMX2485E RF PLL: 50 MHz to 3.0 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 to 3.6 V Operation With ICC = 5.0 mA
  • 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
      Modulator
  • Features for Improved Lock Time
    • Fastlock / Cycle Slip Reduction With Integrated
      Time-Out Counter Which Requires Only a
      Single-Word Write
  • Wide Operating Range
    • LMX2485 RF PLL: 500 MHz to 3.0 GHz
    • LMX2485E RF PLL: 50 MHz to 3.0 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 to 3.6 V Operation With ICC = 5.0 mA

The LMX2485 device is a low power, high performance delta-sigma fractional-N PLL with an auxiliary integer-N PLL. The device is fabricated using Texas Instruments’ 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 LMX2485 is highly resistant to changes in temperature and variations in wafer processing. The LMX2485 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 LMX2485 is transferred through a three-line, high-speed (20-MHz) MICROWIRE interface. The LMX2485 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 LMX2485 is available in a 24-lead 4.0 × 4.0 × 0.8 mm WQFN package.

The LMX2485 device is a low power, high performance delta-sigma fractional-N PLL with an auxiliary integer-N PLL. The device is fabricated using Texas Instruments’ 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 LMX2485 is highly resistant to changes in temperature and variations in wafer processing. The LMX2485 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 LMX2485 is transferred through a three-line, high-speed (20-MHz) MICROWIRE interface. The LMX2485 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 LMX2485 is available in a 24-lead 4.0 × 4.0 × 0.8 mm WQFN package.
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Technical documentation

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Type Title Date
* Data sheet LMX2485x 3-GHz Delta-Sigma Low-Power Dual PLLatinum Frequency Synthesizer datasheet (Rev. G) PDF | HTML 13 Jan 2016
Application note AN-1879 Fractional N Frequency Synthesis (Rev. B) 18 Nov 2021
EVM User's guide LMX248x Evaluation Board User's Guide (Rev. B) 27 Jul 2018

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