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LMX2486 Datasheet(PDF) 1 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor. Click here to check the latest version.
Part No. LMX2486
Description  1.0 GHz - 4.5 GHz High Performance Delta-Sigma Low Power Dual PLLatinum TM Frequency Synthesizers with 3.0 GHz Integer PLL
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Maker  NSC [National Semiconductor (TI)]
Homepage  http://www.national.com
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LMX2486 Datasheet(HTML) 1 Page - National Semiconductor (TI)

 
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LMX2486
1.0 GHz - 4.5 GHz High Performance Delta-Sigma Low
Power Dual PLLatinumFrequency Synthesizers with
3.0 GHz Integer PLL
General 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 National Semiconductor’s advanced pro-
cess.
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 process-
ing. 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 modula-
tion 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 LLP package.
Applications
n
Cellular phones and base stations
CDMA, WCDMA, GSM/GPRS, TDMA, EDGE, PDC
n
Direct digital modulation applications
n
Satellite and cable TV tuners
n
WLAN Standards
Features
Quadruple Modulus Prescalers for Lower Divide Ratios
n
RF PLL: 16/17/20/21 or 32/33/36/37
n
IF PLL: 8/9 or 16/17
Advanced Delta Sigma Fractional Compensation
n
12 bit or 22 bit selectable fractional modulus
n
Up to 4th order programmable delta-sigma modulator
Features for Improved Lock Times and Programming
n
Fastlock / Cycle slip reduction
n
Integrated time-out counter
n
Single word write to change frequencies with Fastlock
Wide Operating Range
n
LMX2486 RF PLL: 1.0 GHz to 4.5 GHz
Useful Features
n
Digital lock detect output
n
Hardware and software power-down control
n
On-chip crystal reference frequency doubler.
n
RF phase comparison frequency up to 50 MHz
n
2.5 to 3.6 volt operation with I
CC = 8.5 mA at 3.0 V
Functional Block Diagram
20156901
PLLatinumis a trademark of National Semiconductor Corporation.
January 2006
© 2006 National Semiconductor Corporation
DS201569
www.national.com


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