IMI-FS79/1/2/4
LOW EMI SPECTRUM SPREAD CLOCK
Approved Product
Features
Applications
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Spread Spectrum Clock Generator (SSCG)
with 1x, 2x and 4x Outputs
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Desktop/Notebook Computers
VGA, XGA and SXGA LCD Displays
High Speed Printers and Copiers
CD-ROM, VCD and DVD
Embedded Systems
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80 to 140 MHz operating frequency range.
Modulates external clocks including crystals,
crystal oscillators and ceramic resonators.
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Programmable modulation with simple
R-C external loop filter (LF)
Center Spread Modulation.
3 - 5 Volt power supply.
Networking, LAN/WAN
Modems
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Benefits
TTL/CMOS compatible outputs.
Low short term jitter.
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Programmable EMI Reduction
Fast Time to Market
Low Power Dissipation;
Lower cost of compliance
3.3 VDC = 73 mw - typical
5.0 VDC = 225 mw - typical
Available in 8 pin SOIC package.
No degradation in Rise/Fall times
Lower component and PCB layer count
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Product Description
internally by the input frequency and the selected
input frequency range.
The IMI FS791/2/4 are Spread Spectrum Clock
Generator ICs (SSCG) designed for the purpose of
reducing Electro Magnetic Interference (EMI) found
in today’s high-speed digital systems.
The Bandwidth of these products can be
programmed from as little as 0.6% up to as much as
4.0% by selecting the proper loop filter value. Refer
to the Loop Filter Selection chart on page 5 for
recommended values. Due to a wide range of
application requirements, an external loop filter (LF)
is used on the FS79x products.
The FS791/2/4 SSCG clocks use an IMI proprietary
technology to modulate the input clock frequency,
FSOUT by modulating the frequency of the digital
clock. By modulating the reference clock the
measured EMI at the fundamental and harmonic
frequencies of FSOUT is greatly reduced. This
reduction in radiated energy can significantly reduce
the cost of complying with regulatory requirements
without degrading digital waveforms.
The user can select the exact amount of frequency
modulation suitable for the application.
Using a
fixed internal loop filter would severely limit the use
of a wide range of modulation bandwidths (Spread
%) to a few discrete values.
The FS791/2/4 are designed to operate over a very
wide range of input frequencies and provides 1x, 2x
and 4x modulated clock outputs.
The IMI FS791/2/4 Spread Spectrum Clock
Generator (SSCG) products are versatile devices to
use in a wide range of applications.
Refer to FS781/2/4 products for applications
requiring 6 to 82 MHz frequency range.
The bandwidth of the frequency spread at FSOUT is
determined by the values of the loop filter
components. The modulation rate is determined
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.
MILPITAS, CA 95035 (408) 263-6300 FAX: (408) 263-6571
http://www.imicorp.com
Rev 1.1
7/20/1999
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