LMX2485Q-Q1_15 Datasheet, PDF (1/40 Pages) Texas Instruments – LMX2485Q 500 MHz - 3.1 GHz High Performance Delta-Sigma Low Power DualPLLatinum™ Frequency Synthesizers with 800 MHz Integer PLL

www.ti.com
SNOSCP7 – MARCH 2013
LMX2485Q 500 MHz - 3.1 GHz High Performance Delta-Sigma Low Power Dual
PLLatinum™ Frequency Synthesizers with 800 MHz Integer PLL
Check for Samples:
FEATURES
1
•23 Quadruple Modulus Prescalers for Lower
Divide Ratios
– 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 Times and
Programming
– Fastlock / Cycle Slip Reduction
– Integrated Time-out Counter
– Single Word Write to Change Frequencies
with Fastlock
• Wide Operating Range
– LMX2485Q RF PLL: 500 MHz to 3.1 GHz
• Useful Features
– Digital Lock Detect Output
– Hardware and Software Power-down
Control
– On-chip Crystal Reference Frequency
Doubler.
– RF Phase Comparison Frequency up to 50
MHz
– 2.5 to 3.6 Volt Operation with I_CC = 5.0 mA
at 3.0 V
– LMX2485Q is AEC-Q100 Grade 2 Qualified
and is Manufactured on an Automotive
Grade Flow
APPLICATIONS
• Cellular Phones and Base Stations
– CDMA, WCDMA, GSM/GPRS, TDMA, EDGE,
PDC
• Direct Digital Modulation Applications
• Satellite and Cable TV Tuners
• WLAN Standards
DESCRIPTION
The LMX2485Q 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 is highly
resistant to changes in temperature and variations in
wafer processing. The LMX2485Q 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 is
transferred via a three line high speed (20 MHz)
MICROWIRE interface. The LMX2485Q 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
is available in a 24 lead 4.0 X 4.0 X 0.8 mm WQFN
package.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PLLatinum is a trademark of Texas Instruments.
2
All other trademarks are the property of their respective owners.
3
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2013, Texas Instruments Incorporated