October 2003
rev 1.0
Peak Reducing EMI Solution
Features
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FCC approved method of EMI
attenuation.
Provides up to 15dB EMI reduction.
Generates a low EMI spread spectrum
clock and a non-spread reference clock
of the input frequency.
Optimized for frequency range from
20MHz to 40MHz.
Internal loop filter minimizes external
components and board space.
Selectable spread options: Down and
Center Spread.
Low inherent cycle-to-cycle jitter.
ASM3P1819A-H
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Eight Spread % Selections:
o
± 0.625% to –3.5%.
3.3V operating voltage.
CMOS/TTL compatible inputs and
outputs.
Low-power CMOS design.
Supports notebook VGA and other LCD
timing controller applications.
Power down function for mobile
application.
Products are available for industrial
temperature range.
Available in 8-pin SOIC and TSSOP
packages.
Product Description
The ASM3P1819x is a versatile spread
spectrum
frequency
modulator
designed
specifically for input clock frequencies from
20MHz to 40MHz. The ASM3P1819x can
generate an EMI reduced clock form an OSC or
a system-generated clock. The ASM3P1819x
offers Down and Center spread options with
different percentage deviations.
(Refer Spread
Deviation Selections Table.)
The ASM3P1819x reduces electromagnetic
interference (EMI) at the clock source, allowing
system wide reduction of EMI of down stream
clock and data dependent signals. The
ASM3P1819x allows significant system cost
savings by reducing the number of circuit board
layers and shielding that are traditionally
required to pass EMI regulations.
The ASM3P1819x modulates the output of a
single PLL in order to “spread” the bandwidth of
a synthesized clock, thereby decreasing the
peak amplitudes of its harmonics. This results in
significantly lower system EMI compared to the
typical narrow band signal produced by
oscillators and most clock generators. Lowering
EMI by increasing a signal’s bandwidth is called
spread spectrum clock generation.
The ASM3P1819x uses the most efficient and
optimized modulation profile approved by the
FCC and is implemented by using a proprietary
all-digital method.
Applications
The ASM3P1819x is targeted towards EMI
management for memory and LVDS interfaces
in mobile graphic chipsets and high-speed digital
applications such as PC peripheral devices,
consumer electronics, and embedded controller
systems.
Alliance Semiconductor
2595, Augustine Drive
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Santa Clara
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CA 95054
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Tel 408 855 4900
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Fax 408 855 4999
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www.alsc.com
Notice: The information in this document is subject to change without notice.
PULSECORE [ PulseCore Semiconductor ]
