July 2005

P2008A

rev 1.3

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.

General Purpose EMI Reduction IC

Features

FCC approved method of EMI attenuation.

Provides up to 15dB of EMI suppression.

Generates a 1X or ½ X low EMI spread spectrum

clock of the input frequency.

Input frequency range: 4MHz to 32MHz.

Internal loop filter minimizes external components

and board space.

Spreading ranges from ±0.8% to ±3.2%.

SSON# control pin for spread spectrum enable

and disable options.

Low Cycle-to-Cycle jitter.

3.3V Operating Voltage.

Ultra-low power CMOS design.

Available in 8-pin SOIC and TSSOP Packages.

Product Description

The P2008A is a versatile spread spectrum frequency

modulator designed specifically for digital camera and

other digital video and imaging applications. The P2008A

reduces electromagnetic interference (EMI) at the clock

source, allowing system wide reduction of EMI of down

stream clock and data dependent signals. The P2008A

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 P2008A uses the most efficient and optimized

modulation profile approved by the FCC and is

implemented in a proprietary all digital method.

The P2008A 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 P2008A is targeted towards cable, xDSL, fax

modem, set-top box, USB controller, DSC, and other

embedded systems.

Block Diagram

VSS

VDD

XIN/CLKIN

Frequency

Divider

Feedback

Divider

Modulation

Phase

Detector

Loop

Filter

VCO

Output

Divider

ModOUT

PLL

SSON#

DIV2

SR0

Crystal

Oscillator

XOUT