
November 2003
rev 1.1
ASM3P2182A
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.
LCD Panel EMI Reduction IC
Features
FCC approved method of EMI attenuation.
Provides up to 15dB EMI reduction.
Generates a 1X low EMI spread spectrum clock of
the input frequency.
Input frequency range: 25MHz to 210 MHz.
Internal loop filter minimizes external components
and board space.
Center spread.
4 spread frequency deviation selections: ± 0.13%
to ± 1.24%.
Low inherent cycle-to-cycle jitter.
3.3V operating voltage range.
TTL or CMOS compatible inputs and outputs.
Low power CMOS design.
Supports notebook VGA and other LCD timing
controller applications.
Products are available for industrial temperature
range.
Available in 8-pin SOIC and TSSOP.
Product Description
The ASM3P2182A is a versatile spread spectrum
frequency modulator designed specifically for a wide
range of input clock frequencies from 25MHz to 210MHz.
(Refer Input Frequency and Modulation Rate Table)
. The
ASM3P2182A can generate an EMI reduced clock from
an OSC or a system generated clock. The ASM3P2182A
offers a Center Spread clock and with a percentage
deviation from ± 0.13% or ± 1.24%.
The ASM3P2182A reduces electromagnetic interference
(EMI) at the clock source, allowing system wide reduction
of EMI of down stream clock and data dependent
signals. The ASM3P2182A 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.
The ASM3P2182A uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented in a proprietary all digital method.
The ASM3P2182A 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’.
Applications
The ASM3P2182A 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.
Block Diagram
VSS
XIN
Crystal
Oscillator
Divider
Divider
Frequency
Feedback
Modulation
Phase
Detector
Loop
Filter
VCO
Output
Divider
MODOUT
PLL
VDD
S0, S1
FS0 FS1