1998 Product of the Year Award Winner
RF frequency synthesizer slashes
power and parts count in wireless apps
The Si4132 is a single-chip RF frequency synthesizer that promises to
significantly reduce space, cost, and power requirements in wireless handset
designs. These benefits, so critical in portable equipment, were achieved
through an innovative mixed-signal design that integrates a variety of
functions using standard digital CMOS processes.
When introduced in October, the device was called the industry's most
complete RF frequency synthesizer. The chip generates RF frequencies in
two bands–600 MHz to 1.3 GHz and 1.3 to 1.8 GHz–as well as IF frequencies
of 50 to 600 MHz.
By implementing a complete RF frequency synthesizer in standard digital
CMOS processes, Silicon Laboratories produced an RF frequency synthesizer
that provides significant savings in size, cost, and power for wireless handset designs.
According to the company, the Si4132 reduces board space requirements
by 75% and system cost by 30% in handset designs. The number of components
needed for frequency synthesis drops from the more than 35 parts used in
previous designs to just one IC and four passive components. The complete
synthesizer design occupies less than 150 mm2 of board space.
In part, the synthesizer's high level of integration is made possible
by the company's ability to incorporate tuning elements–such as varactor
diodes and resonators–on chip. These components are combined with VCOs,
loop filters, reference and VCO dividers, and phase detectors in a 24-pin
TSSOP. Variables for dividers, prescalers, and power-down settings are
programmable through a three-wire serial interface.
Low power consumption and fast lock times are other benefits. Operating
from a 2.7 to 3.6-V supply, the synthesizer draws 18 mA in typical operation.
Differences in performance requirements such channel spacing, frequency
range, and phase noise make it difficult for one frequency synthesizer
to work in all dual-band wireless applications. The Si4132 has been optimized
for the GSM market and the company is currently developing two related
versions to serve the cellular/PCS IS-136 market (Si4134) and the CDMA
market (Si4135).
In addition, the company is offering lower-cost derivatives of the Si4132
for customers who require only one or two phase-locked loops. Samples of
the Si4132 are typically provided as part of the Si4132-EVB evaluation
board. ($6.50 ea/10,000; Si4132-EVB, $150–samples available now; prod
qty available 1st qtr 1999.)
Silicon Laboratories
Austin, TX
Gary Gay 512-416-8500
Fax 512-416-9669
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