LMX2364
2.6 GHz PLLatinum Fractional RF Frequency Synthesizer
with 850 MHz Integer IF Frequency Synthesizer
General Description
The LMX2364 integrates a high performance 2.6 GHz fractional frequency synthesizer with a 850 MHz low power
Integer-N frequency synthesizer. Designed for use in a local
oscillator subsystem of a radio transceiver, the LMX2364
generates very stable, low noise control signals for UHF and
VHF voltage controlled oscillators. It is fabricated using National’s high performance BiCMOS process.
The RF Synthesizer supports both fractional and integer
modes. The N counter contains a selectable, quadruple
modulus prescaler and can support fractional denominators
from 1 to 128. A flexible, 4 level programmable charge pump
supplies output current magnitudes ranging from 1 mA to 16
mA. Only a single word write is required to power up and
tune the synthesizer to a new frequency.
High performance FastLock™ technology makes the
LMX2364 an excellent choice for applications requiring aggressive lock time while maintaining excellent phase noise
and spurious performance. The combination of the improved
FastLock circuitry, the enhanced fractional compensation
engine, and the programmable charge pump architecture
gives the designer maximum freedom to optimize the performance of the synthesizer for the target application. Integrated timeout counters greatly simplify the programming
aspects of FastLock. These timeout counters reduce the
demands on the microcontroller by automatically disengaging FastLock after a perscribed number of reference cycles
of the phase detector.
The IF synthesizer includes a fixed 8/9 dual modulus prescaler, a two level programmable charge pump, and dedicated FastLock circuitry with an integrated timeout counter.
The LMX2364 offers many performance enhancements over
the LMX2354. Improvements in the fractional compensation
make the spurs on the LMX2364 approximately 6 dB better
in a typical application. The higher and more flexible fractional modulus combined with the higher charge pump currents result in phase noise improvements on the order of 10
dB. The cycle slip reduction circuitry of the LMX2364 is both
easy to use and effective in reducing cycle slipping and
allows one to use very high phase detector frequencies
without degrading lock times.
Serial data is transferred to the device via a three-wire
interface (DATA, LE, CLK). The low voltage logic interface
allows direct connection to 1.8 Volt and 3.0 Volt devices.
Supply voltages from 2.7V to 5.5V are supported. Independent charge pump supplies for each synthesizer allows the
designer to optimize the bias level for the selected VCO. The
LMX2364 consumes 5.0 mA (typical) of current in integer
mode and 7.2 mA (typical) in fractional mode. The LMX2364
is available in a 24 Pin Ultra Thin CSP package and 24 Pin
TSSOP Package.
Features
n RF Synthesizer supports both Fractional and Integer
Operating Modes
n Pin Compatible upgrade for LMX2354
n 2.7V to 5.5V operation
n Pin and programmable power down
n Fractional N divider supports fractional denominators
ranging from 1 through 128
n Supports Integer Mode Operation
n Programmable charge pump current levels
RF: 4 level, 1 – 16 mA
IF: 2 level, 100/800 uA
n FastLock Technology with integrated timeout counters
n Digital filtered & analog lock detect output
n FastLock Glitch Reduction Technology
n Enhanced Low Noise Fractional Compensation Engine
n Low voltage programming interface allows direct
connection to 1.8V logic
Applications
n
n
n
n
n
n
n
n
n
Digital Cellular
GPRS
IS-136
GAIT
PDC
EDGE
CDMA
Zero blind slot TDMA systems
Cable TV Tuners (CATV)
FastLock™ is a trademark of National Semiconductor Corporation.
TRI-STATE ® is a registered trademark of National Semiconductor Corporation.
© 2003 National Semiconductor Corporation
DS200506
www.national.com
LMX2364 2.6 GHz PLLatinum Fractional RF Frequency Synthesizer with 850 MHz Integer-N IF
Frequency Synthesizer
July 2003