LMX2305TMX

Clock Generators, PLLs, Frequency Synthesizers Overview

The LMX2305TMX is a PLLatinum frequency synthesizer designed for RF personal communications, operating up to 550 MHz. It utilizes an ABiC IV BiCMOS process and features a dual modulus prescaler with selectable divide ratios of 64/65 or 128/129. The device operates on a supply voltage ranging from 2.65 V to 5.5 V, with typical current consumption of 4.0 mA at 2.75 V. It includes an internal balanced charge pump and communicates via a three-line MICROWIRE interface. The component is housed in a 20-lead TSSOP surface-mount package.

Clock Generators, PLLs, Frequency Synthesizers Feature Summary

• Dual modulus prescaler supporting 64/65 or 128/129 divide ratios for flexible frequency synthesis
• Integrated balanced low leakage charge pump for stable loop filter driving
• Three-line MICROWIRE serial interface for programmable reference and N counters
• Power down mode capability for reduced current consumption during standby

Clock Generators, PLLs, Frequency Synthesizers Applications

• Analog cellular telephone systems (AMPS, ETACS, NMT)
• Portable wireless communications including PCS/PCN and cordless devices
• Wireless local area networks (WLANs)
• Pager systems

Clock Generators, PLLs, Frequency Synthesizers Procurement Notes

Verify the obsolete status of this component before procurement planning. Texas Instruments has discontinued the LMX2305 series. Confirm availability through authorized distributors or secondary markets. Ensure that any replacement components meet the original system specifications for frequency range, package dimensions, and electrical characteristics to maintain design integrity.

Clock Generators, PLLs, Frequency Synthesizers Selection Notes

Select this component only if legacy support for analog cellular standards like AMPS or NMT is required. The 550 MHz upper frequency limit restricts usage in modern wideband applications. Consider the 20-pin TSSOP footprint for board layout compatibility. Evaluate the need for external charge pumps if stringent phase noise or spur requirements exceed the internal pump capabilities.

Clock Generators, PLLs, Frequency Synthesizers Part Context

The LMX2305 belongs to the National Semiconductor PLLatinum family, now managed by Texas Instruments following their acquisition. This specific part was engineered for cost-effective RF front-end solutions in the late 1990s. It represents an earlier generation of fractional-N synthesizers compared to modern broadband alternatives, focusing on simplicity and low power for dedicated cellular bands.

Clock Generators, PLLs, Frequency Synthesizers Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Due to the obsolete status, engineers must perform a full redesign or source surplus inventory. Potential replacements should be identified based on specific frequency coverage and package constraints rather than direct pin-to-pin compatibility.