June 1999
LMX2350/LMX2352
PLLatinum™ Fractional N RF / Integer N IF
Dual Low Power Frequency Synthesizer
2352 family features very low current consumption; typically
LMX2350 (2.5 GHz) 6.75 mA, LMX2352 (1.2 GHz) 5.00 mA
at 3.0V. The LMX2350/2352 are available in a 24-pin TSSOP
surface mount plastic package.
LMX2350 2.5 GHz/550 MHz
LMX2352 1.2 GHz/550 MHz
General Description
The LMX2350/2352 is part of a family of monolithic integrated fractional N/ Integer N frequency synthesizers designed 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 generate very stable low noise control signals for UHF and VHF
voltage controlled oscillators (VCO’s).
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/
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
n
n
n
n
n
Applications
Portable wireless communications (PCS/PCN, cordless)
Dual mode cellular telephone systems
Zero blind slot TDMA systems
Spread spectrum communication systems (CDMA)
Cable TV Tuners (CATV)
Block Diagram
DS100831-1
FastLock™ is a trademark of National Semiconductor Corporation.
MICROWIRE™ is a trademark of National Semiconductor Corporation.
PLLatinum™ is a trademark of National Semiconductor Corporation.
TRI-STATE ® is a registered trademark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation
DS100831
www.national.com
LMX2350/LMX2352 PLLatinumTM Fractional N RF / Integer N IF Dual Low Power Frequency
Synthesizer
PRELIMINARY