LMX2486_14 Datasheet, PDF (1/41 Pages) Texas Instruments – 1.0 GHz - 4.5 GHz High Performance Delta-Sigma Low Power Dual PLLatinum™ Frequency Synthesizers with 3.0 GHz Integer PLL

LMX2486
www.ti.com
SNAS324 – JANUARY 2006
LMX2486 1.0 GHz - 4.5 GHz High Performance Delta-Sigma Low Power Dual PLLatinum™
Frequency Synthesizers with 3.0 GHz Integer PLL
Check for Samples: LMX2486
FEATURES
1
•23 Quadruple Modulus Prescalers for Lower
Divide Ratios
– RF PLL: 16/17/20/21 or 32/33/36/37
– 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
– LMX2486 RF PLL: 1.0 GHz to 4.5 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 = 8.5 mA
at 3.0 V
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 LMX2486 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 LMX2486 is highly
resistant to changes in temperature and variations in
wafer processing. The LMX2486 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 LMX2486 is
transferred via a three line high speed (20 MHz)
MICROWIRE interface. The LMX2486 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 LMX2486 is
available in a 24 lead 4.0 X 4.0 X 0.8 mm WQFN
package.
Functional Block Diagram
FinIF
ENOSC
OSCin
OSCout
VddRF1
VddRF2
VddRF3
VddRF4
VddRF5
FinRF
FinRF*
CE
CLK
DATA
LE
1X / 2X
IF N Divider
8/9
or
16/17
Prescaler
B Counter
A Counter
IF R
Divider
RF R
Divider
RF N Divider
16/17/20/21 C Counter
32/33o/r3R6/F3N7 ^{DividBerCounter}
Prescaler
A Counter
MICROWIRE
Interface
6'
Compensation
Phase
Comp
IF
LD
RF LD
Phase
Comp
Charge
Pump
Ftest/LD
MUX
Charge
Pump
RF Fastlock
VddIF1
VddIF2
CPoutIF
Ftest/LD
CPoutRF
FLoutRF
GND
GND
GND
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 © 2006, Texas Instruments Incorporated