September 2003

ASM3P2183A

rev 1.0

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.

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: 6MHz to 103MHz.

Internal loop filter minimizes external components

and board space.

Selectable spread options: Down and Center

Spread

2 spread frequency deviation selections:

o

-1.25% or ± 0.42%

Low inherent cycle-to-cycle jitter.

3.3V operating voltage range.

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 ASM3P2183 is a versatile spread spectrum

frequency modulators designed specifically for a wide

range of input clock frequencies from 6MHz to 103MHz.

(Refer Input Frequency and Modulation Rate Table)

. The

ASM3P2183A can generate an EMI reduced clock from

an OSC or a system generated clock. The ASM3P2183A

offers a Down Spread clock with a percentage deviation

of -1.25% and a Center Spread clock with a percentage

deviation of ± 0.42%.

The ASM3P2183A reduces electromagnetic interference

(EMI) at the clock source, allowing system wide reduction

of EMI of

down stream clock and data dependent

signals. The ASM3P2183A 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 ASM3P2183A uses the most efficient and optimized

modulation profile approved by the FCC and is

implemented in a proprietary all digital method.

The ASM3P2183A 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 ASM3P2183A 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.