wireless communications products Dual Fractional-N Synthesizer PLL Family™ CX72300/CX72301/ CX72302 and CX74038 Conexant’s synthesizer phase-locked loop (PLL) family, which comprises the CX72300, CX72301, CX72302 and CX74038 dual fractional-N synthesizers, sets a benchmark for performance and functionality. These fractional-N synthesizer ICs resolve output frequency step sizes below 100 Hz. As precision tuners in next-generation narrowband and multiband digital radio products, these chips overcome the traditional trade-off associated with obtaining ultra-fine frequency resolution and low-phase noise performance. Alternative solutions are unable to resolve step sizes below 200 KHz without dividing the crystal reference frequency many times, a technique that induces unwanted phase noise, degrades signal integrity and contributes to the cost of radio systems, potentially forcing designers to use a more expensive voltage controlled oscillator (VCO). While other solutions sacrifice phase noise performance to increase resolution, Conexant’s fractional-N synthesizer family employs a high internal reference and delta- Distinguishing Features sigma (DS) technology to achieve both excellent phase noise performance and fine frequency resolution in a single chip. • Industry’s most comprehensive dual fractional-N synthesizer family In addition to offering fine frequency step size and low phase • Fast settling time (down to 100µs) noise, the Conexant synthesizer PLL family offers fast frequency • Ultra-fine step size of 100 Hz or less settling time, a performance feature required by current and • Phase noise as low as -95 dBc/Hz future wireless network applications such as GPRS and W-CDMA. • Low spurious noise This feature enables such applications to send a signal and quickly reset to send another signal to meet data throughput requirements. features and specifications The Design Solution CX72300 Specific Performance RF engineers face many design problems when using • Dual 2.1 GHz Main/RF & 500 MHz Auxiliary/IF Synthesizer traditional integer-N synthesizers to build multimode • Low phase noise -91 dBc/Hz @ 1800 MHz measured inside the loop bandwidth or narrowband circuits. Phase noise is often the most important design consideration. When their requirements call for a fine step size, designers must divide the reference CX72301 Specific Performance: frequency to achieve a lower comparison frequency. This • Dual 1.0 GHz Main/RF & 500 MHz Auxiliary/IF Synthesizer problem of low comparison frequency can be avoided • Low phase noise -96 dBc/Hz @ 950 MHz measured inside using fractional-N techniques that employ DS technology. the loop bandwidth These techniques allow the designer to maintain a high comparison frequency, which in turn permits low CX72302 Specific Performance: phase noise. • Dual 6.1 GHz Main/RF & 1.0 GHz Auxiliary/IF Synthesizer • Low phase noise -80 dBc/Hz @ 6.1 GHz measured inside Radio designers, in order to meet systems specifications, the loop bandwidth' must often resort to very narrow loop filter bandwidths. contributions. Conexant’s fractional-N synthesizers allow CX74038 Dual Fractional-N/Interger-N Frequency Synthesizer designers to lower VCO noise, by widening the loop filter The Conexant CX74038 2.6 GHz/800 MHz dual frequency bandwidth. Switching speed is also a primary concern of synthesizer is a complete, low power synthesizer IC tailored next generation handset and base station manufacturers. specifically for portable/battery operation. Housed in a tiny The larger the loop frequency, the faster the switching speed. 3.5mm x 4.5mm chip scale package (also available in 20-pin This is done at the cost of increasing the VCO phase noise TSSOP) the CX74038 fractional-N performance offers low phase noise and fast settling time necessary for use in next CX72300/01/02 Dual Fractional-N Synthesizers generation handset applications. The CX7230x synthesizers are ideal for applications that need low phase noise, fine channel step size and fast CX74038 features: switching speeds. Offering performance that meets • Low power consumption for portable/handset stringent system requirements for a broad range of applications applications, these products are suited for use in next • Supply voltage as low as 2.6V generation base stations, tactical radios, test equipment • Very fast switching speed (sub 100 us) and instrumentation, satellite receivers and low bit rate • Step size <5 Hz @ 2.6 GHz FM/FSK/MSK/GMSK telemetry transmitters (Direct Digital • Dual 2.6 GHz Main/RF and 800 MHz Auxiliary/ Modulation feature). IF Synthesizer Features common to this family are: • Spur-free operation • Step size <100 Hz (<400 Hz for -CX72302) • Very fast switching speed (<100 us) • On-chip oscillator circuit • Direct Digital Modulation • 28-pin TSSOP www.conexant.com © 2001, Conexant Systems, Inc. All Rights Reserved. General Information: Conexant and the Conexant logo are trademarks of Conexant Systems, Inc. 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