September 2004
rev 1.0
ASM3P2180A
Peak Reducing EMI Solution
Features
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.
•
Generates an EMI optimized clocking
signal at the output.
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•
Selectable output frequency range.
Single 1.25% or 2.4% down spread
The ASM3P2180A uses the most efficient and
optimized modulation profile approved by the
FCC and is implemented by using a proprietary
all-digital method.
output.
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•
•
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Integrated loop filter components.
Operates with a 3.3V supply.
Low-power CMOS design.
Applications
Available in 8-pin SOIC and 8-pin
TSSOP packages.
The ASM3P2180A is targeted towards notebook
LCD displays, other displays using an LVDS
interface, PC peripheral devices and embedded
systems.
Product Description
The ASM3P2180A is
a
versatile Spread
Spectrum frequency modulator designed
Key Specifications
specifically for
a
wide range of clock
ASM3P2180A reduces
frequencies. The
electromagnetic interference (EMI) at the clock
source, allowing system wide reduction of EMI
of down stream clock and data dependent
signals. The ASM3P2180A allows significant
system cost savings by reducing the number of
circuit board layers and shielding that are
traditionally required to pass EMI regulations.
Description
Supply voltages
Specification
VDD = 3.3V ± 5%
6 MHz ≤ Fin ≤10 MHz
FS1=0
FS1=1
Frequency
range
18 MHz ≤ Fin ≤ 30 MHz
Cycle-to-cycle jitter
Selectable spread percentage
Output duty cycle
325 pS (max)
-1.25% or –2.4%
45/55% (worst case)
5ns (maximum)
The ASM3P2180A 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
Output rise and fall time
Simplified Block Diagram
3.3V
X1
ASM3P2180A
X2
Spread spectrum output
(EMI suppressed)
Alliance Semiconductor
2595, Augustine Drive • Santa Clara • CA 95054 • Tel 408 855 4900 • Fax 408 855 4999 • www.alsc.com
Notice: The information in this document is subject to change without notice.
ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
