September 2003
rev 1.0
ASM3P2811A/B
ASM3P2812A/B
ASM3P2814A/B
Low Power EMI Reduction IC
Features
deviation range from ±0.625% to –3.50%.
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FCC approved method of EMI attenuation.
Provides up to 15dB EMI reduction.
The ASM3P28XX reduces electromagnetic interference
(EMI) at the clock source, allowing system wide reduction
of EMI of down stream clock and data dependent
signals. The ASM3P28XX allows significant system cost
savings by reducing the number of circuit board layers,
ferrite beads, shielding, and other passive components
that are traditionally required to pass EMI regulations.
Generates a 1X, 2X and 4X low EMI spread
spectrum clock of the input frequency.
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1X: ASM3P2811A/B
2X: ASM3P2812A/B
4X: ASM3P2814A/B
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Optimized for input frequency range from 10MHz
to 40 MHz.
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ASM3P2811A/B: 10 to 40MHz
ASM3P2812A/B: 10 to 40MHz
ASM3P2814A/B: 10 to 40MHz
The ASM3P28XX modulates the output of a single PLL in
order to “spread” the bandwidth of a synthesized clock,
and more importantly, decreases 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 frequency generators. Lowering
EMI by increasing a signal’s bandwidth is called ‘spread
spectrum clock generation’.
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Internal loop filter minimizes external components
and board space.
Selectable spread options: Down Spread and
Center Spread.
8 spread frequency deviation selections:
o
±0.625% to –3.5%
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Low inherent cycle-to-cycle jitter.
3.3V operating voltage range.
The ASM3P28XX uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented in a proprietary all-digital method.
CMOS/TTL compatible inputs and outputs.
Pinout compatible with Cypress CY25811,
CY25812 and CY25814.
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Products are available for industrial temperature
range.
Applications
The ASM3P28XX 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.
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Available in 8-pin SOIC and TSSOP.
Product Description
The ASM3P28XX devices are versatile spread spectrum
frequency modulators designed specifically for a wide
range of input clock frequencies from 10MHz to 40MHz.
(Refer Input/Output Frequency Range Selection Table).
The ASM3P28XX can generate an EMI reduced clock
from crystal, ceramic resonator, or system clock. The
ASM3P28XX-A and the ASM3P28XX-B offer various
combinations of spread options and percentage
deviations (Refer Output Frequency Deviation and
Spread Option Selection Table). These combinations
include Down and Center Spread and percentage
Alliance Semiconductor
2575, Augustine Drive • Santa Clara, CA • Tel: 408.855.4900 • Fax: 408.855.4999 • www.alsc.com
Notice: The information in this document is subject to change without notice.
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