October 2003

P2005A/S

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.

Low Frequency 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: 8MHz to 32MHz.

Internal loop filter minimizes external components

and board space.

Frequency deviation:

o

P2005A: ± 1% to ± 3%

o

P2005S: ± 0.6% to ± 1.8%

SSON# control pin for spread spectrum enable

and disable options.

Low cycle-to-cycle jitter.

3.3V or 5V operating voltage range.

16mA output drives.

TTL or CMOS compatible outputs.

Ultra-low power CMOS design.

Available in 8-pin SOIC and TSSOP.

Product Description

The P2005X is a versatile spread spectrum frequency

modulator

designed

specifically

for

input

clock

frequencies from 8MHz to 32MHz. Refer Output

Frequency Selection Table.

The P2005X can generate an

EMI reduced clock from crystal, ceramic resonator, or

system clock. The P2005X offers various percentage

deviations ranging form ±0.6% to ±3.0%. Refer

Frequency Deviation Selections Table.

The P2005X

reduces electromagnetic interference (EMI) at the clock

source, allowing system wide reduction of EMI of down

stream clock and data dependent signals. The P2005X

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 P2005X uses the most efficient and optimized

modulation profile approved by the FCC and is

implemented in a proprietary all digital method.

The P2005X 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 P2005X is targeted towards EMI management for

high-speed digital applications such as PC peripheral

devices, consumer electronics and embedded controller

systems.

Block Diagram

VSS

XIN

Frequency

Divider

Feedback

Divider

Modulation

Phase

Detector

Loop

Filter

VCO

Output

Divider

MODOUT

PLL

VDD

SSON#

DIV2

SR0

Crystal

Oscillator

XOUT