LMX2354

The LMX2354 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 0.5 µ ABiC V silicon BiCMOS process. The LMX2354 contains quadruple modulus prescalers along with modulo 15 or 16 fractional compensation circuitry in the RF divider. The LMX2354 provides a continuous divide ratio of 80 to 32767 in 16/17/20/21 (1.2 GHz2.5 GHz) fractional mode and 40 to 16383 in 8/9/12/13 (550 MHz1.2 GHz) fractional mode. The IF circuitry for the LMX2354 contains an 8/9 prescaler, and is fully programmable.

Using a fractional N phase locked loop technique, the LMX2354 can generate 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 100 µA to 1.6 mA. Two uncommitted CMOS outputs can be used to provide external control signals, or configured to FastLock mode. Serial data is transferred into the LMX2354 via a three wire interface (Data, LE, Clock). Supply voltage can range from 2.7V to 5.5V. The LMX2354 family features very low current consumption; typically LMX2354 (2.5 GHz) - 7.0 mA. The LMX2354 are available in a 24-pin TSSOP surface mount plastic package and 24-pin CSP.