LMX2350

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 radiotransceiver. It is fabricated using National's 0.5µ ABiC V sili-con BiCMOS process. The LMX2350/2352 contains dualmodulus prescalers along with modulo 15 or 16 fractionalcompensation circuitry in the RF divider. A 16/17 or 32/33prescale ratio can be selected for the LMX2350, and theLMX2352 provides 8/9 or 16/17 prescale ratios. The IF cir-cuitry for both the LMX2350 and LMX2352 contains an 8/9prescaler, and is fully programmable.Using a fractional Nphase locked loop technique, the LMX2350 /52 can gener-ate very stable low noise control signals for UHF and VHFvoltage controlled oscillators (VCO's).

For the RF PLL, a highly flexible 16 level programmablecharge pump supplies output current magnitudes from100µA to 1.6mA. Two uncommitted CMOS outputs can beused to provide external control signals, or configured toFastLock™ mode. Serial data is transferred into theLMX2350/2352 via a three wire interface (Data, LE, Clock).

Supply voltage can range from 2.7 V to 5.5 V. The LMX2350/2352 family features very low current consumption; typicallyLMX2350 (2.5 GHz) 6.75 mA, LMX2352 (1.2 GHz) 5.00 mAat 3.0V. The LMX2350/2352 are available in a 24-pin TSSOPsurface mount plastic package.