LMX2350 Datasheet, PDF (1/21 Pages) National Semiconductor (TI) – PLLatinum TM Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer

March 2001
LMX2350/LMX2352
PLLatinum Fractional N RF / Integer N IF
Dual Low Power Frequency Synthesizer
LMX2350 2.5 GHz/550 MHz
LMX2352 1.2 GHz/550 MHz
General Description
The LMX2350/2352 is part of a family of monolithic inte-
grated fractional N/ Integer N frequency synthesizers de-
signed to be used in a local oscillator subsystem for a radio
transceiver. It is fabricated using National’s 0.5µ ABiC V
silicon BiCMOS process. The LMX2350/2352 contains dual
modulus prescalers along with modulo 15 or 16 fractional
compensation circuitry in the RF divider. A 16/17 or 32/33
prescale ratio can be selected for the LMX2350, and the
LMX2352 provides 8/9 or 16/17 prescale ratios. The IF
circuitry for both the LMX2350 and LMX2352 contains an 8/9
prescaler, and is fully programmable. Using a fractional N
phase locked loop technique, the LMX2350 /52 can gener-
ate very stable low noise control signals for UHF and VHF
voltage controlled oscillators (VCOs).
For the RF PLL, a highly flexible 16 level programmable
charge pump supplies output current magnitudes from
100µA to 1.6mA. Two uncommitted CMOS outputs can be
used to provide external control signals, or configured to
FastLock™ mode. Serial data is transferred into the
LMX2350/2352 via a three wire interface (Data, LE, Clock).
Supply voltage can range from 2.7 V to 5.5 V. The LMX2350/
LMX2352 family features very low current consumption; typi-
cally LMX2350 (2.5 GHz) 6.5 mA, LMX2352 (1.2 GHz) 4.75
mA at 3.0V. The LMX2350/2352 are available in a 24-pin
TSSOP and 24-pin CSP surface mount plastic package.
Features
n 2.7 V to 5.5 V operation
n Low current consumption
LMX2350: Icc = 6.75mA typ at 3v
LMX2352: Icc = 5.00mA typ at 3v
n Programmable or logical power down mode
Icc = 5 µA typ at 3v
n Modulo 15 or 16 fractional RF N divider supports ratios
of 1, 2, 3, 4, 5, 8, 15, or 16
n Programmable charge pump current levels
RF 100µA to 1.6mA in 100µA steps
IF 100µA or 800 µA
n Digital filtered lock detect
Applications
n Portable wireless communications (PCS/PCN, cordless)
n Dual mode cellular telephone systems
n Zero blind slot TDMA systems
n Spread spectrum communication systems (CDMA)
n Cable TV Tuners (CATV)
Block Diagram
© 2001 National Semiconductor Corporation DS100831
DS100831-1
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