LMX2485_16 Datasheet, PDF (1/46 Pages) Texas Instruments – 3-GHz Delta-Sigma Low-Power Dual PLLatinum Frequency Synthesizer

Product
Folder
Sample &
Buy
Technical
Documents
Tools &
Software
Support &
Community
LMX2485, LMX2485E
SNAS236G – OCTOBER 2005 – REVISED JANUARY 2016
LMX2485x 3-GHz Delta-Sigma Low-Power Dual PLLatinum™ Frequency Synthesizer
1 Features
•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
– 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 I_CC = 5.0 mA
2 Applications
• Cellular Phones and Base Stations
• Direct Digital Modulation Applications
• Satellite and Cable TV Tuners
• WLAN Standards
3 Description
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.
Device Information⁽¹⁾
PART NUMBER RF PLL Frequency IF PLL Frequency
LMX2485E
50 - 3000 MHz
75 - 800 MHz
LMX2485
500 - 3000 MHz
75 - 800 MHz
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
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
8/9/12/13
C Counter
or
16/17/2R0/F2N1
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
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.