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LMX2485, LMX2485E
SNAS236G –OCTOBER 2005–REVISED JANUARY 2016
LMX2485x 3-GHz Delta-Sigma Low-Power Dual PLLatinum™ Frequency Synthesizer
1 Features
3 Description
The LMX2485 device is
performance delta-sigma fractional-N PLL with an
auxiliary integer-N PLL. The device is fabricated
using Texas Instruments' advanced process.
a
low power, high
1
•
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
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.
–
–
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
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.
–
–
–
–
–
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
2 Applications
•
•
•
•
Cellular Phones and Base Stations
Direct Digital Modulation Applications
Satellite and Cable TV Tuners
WLAN Standards
Device Information(1)
RF PLL Frequency IF PLL Frequency
PART NUMBER
LMX2485E
50 - 3000 MHz
500 - 3000 MHz
75 - 800 MHz
75 - 800 MHz
LMX2485
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Functional Block Diagram
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1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.