LMX2353  Product Folder

The LMX2353 is a monolithic integrated fractional N frequency synthesizer, 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 LMX2353 contains dual modulus prescalers along with modulo 15 or 16 fractional compensation circuitry in the N divider. A 16/17 or 32/33 prescale ratio can be selected for the LMX2353. Using a fractional N phase locked loop technique, the LMX2353 can generate very stable low noise control signals for UHF and VHF voltage controlled oscillators (VCOs).

The LMX2353 has a highly flexible 16 level programmable charge pump which 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 LMX2353 via a three wire interface (Data, LE, Clock). Supply voltage can range from 2.7 V to 5.5 V. The LMX2353 features very low current consumption; typically 5.5 mA at 3.0V. The LMX2353 is available in a 16-pin TSSOP or a 16-pin CSP surface mount plastic package.

• 2.7 V - 5.5 V operation
• Low Current Consumption I_CC = 5.5 mA typ at V_CC = 3.0 V
• Programmable or Logical Power Down Mode I_CC = 5 µA typ at V_CC = 3.0 V
• Modulo 15 or 16 fractional N divider Supports ratios of 1, 2, 3, 4, 5, 8, 15, or 16
• Programmable charge pump current levels 100 µA to 1.6 mA in 100 µA steps
• Digital Filtered Lock Detect

• Portable wireless communications (PCS/PCN, cordless)
• Zero blind slot TDMA systems
• Cellular and Cordless telephone systems
• Spread spectrum communication systems (CDMA)
• Cable TV Tuners (CATV)