November 2006

ASM3P2108A

rev 0.4

Notice: The information in this document is subject to change without notice.

PulseCore Semiconductor Corporation

1715 S. Bascom Ave Suite 200, Campbell, CA 95008

• Tel: 408-879-9077 • Fax: 408-879-9018

www.pulsecoresemi.com

Peak EMI Reducing Solution

Features

•

FCC approved method of EMI attenuation.

•

Generates a 1X low EMI spread spectrum clock

of the input frequency.

•

Input frequency range: 25MHz to 45MHz.

•

Internal loop filter minimizes external

components and board space.

•

Frequency deviation: - 1.3%( Typ) @32MHz.

•

Low cycle-to-cycle jitter.

•

5.0V ± 5% operating voltage range.

•

TTL or CMOS compatible outputs.

•

Available in 8-pin SOIC and TSSOP Packages.

Product Description

The ASM3P2108A is a versatile spread spectrum

frequency modulator designed specifically for input clock

frequencies from 25MHz to 45MHz. The ASM3P2108A

can generate an EMI reduced clock from crystal, ceramic

resonator, or system clock.

The ASM3P2108A reduces electromagnetic interference

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

of EMI of

down stream clock and data dependent

signals. The ASM3P2108A 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 ASM3P2108A uses the most efficient and optimized

modulation profile approved by the FCC and is

implemented in a proprietary all digital method.

The ASM3P2108A 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 ASM3P2108A is targeted towards EMI management

for high speed digital applications such as PC peripheral

devices, consumer electronics and embedded controller

systems.

Block Diagram

GND

XIN

XOUT

Crystal

Oscillator

Frequency

Divider

Feedback

Divider

Modulation

Phase

Detector

Loop

Filter

VCO

Output

Divider

CLOCKOUT

PLL