P2781/82/84

General Purpose EMI

Reduction IC

©2010 SCILLC.

All rights reserved.

Publication Order Number:

JANUARY 2010 – Rev. 2

P2781/82/84

Features

• Provides up to 15dB of EMI suppression

• FCC approved method of EMI attenuation

• Generates a 1X, 2X, and 4X low EMI spread spectrum

clock of the input frequency

• Input frequency range from 3 to 78MHz

• External loop filter for spread % adjustment

• Spreading ranges from ±0.25% to ±5.0%

• Ultra low cycle-to-cycle jitter

• Zero-cycle slip

• 3.3V operating voltage range

• Ultra-low power CMOS design

• P278xA is available in an 8 pin SOIC Package

Product Description

The P278xA is a versatile spread spectrum frequency

modulator designed specifically for digital camera and other

digital video and imaging applications. The P278xA

reduces electromagnetic interference (EMI) at the clock

source, which provides system wide reduction of EMI of all

clock dependent signals. The P278xA allows significant

system cost savings by reducing the number of circuit

board layers and shielding that are traditionally required to

pass EMI regulations.

The P278xA uses the most efficient and optimized

modulation profile approved by the FCC. The P278xA

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 result 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 P278xA is targeted towards MFP, xDSL, fax modem,

set-top box, USB controller, DSC, and embedded systems.

Block Diagram

Crystal

Oscillator

Frequency

Divider

Feedback

Divider

Phase

Detector

Modulation

Output

Divider

VCO

XIN / CLKIN

XOUT

FS0

FS1

LF

VDD

VSS

PLL

ModOUT