Alliance Semiconductor

2575 Augustine Drive

• Santa Clara CA • Tel: 408-855-4900 • Fax: 408-855-4999 • www.alsc.com

rev 0.1

May 2005

ASM3P2111B

Peak EMI Reducing Solution

Features

Generates an EMI optimized clock at the output.

Input frequency: 25 MHz.

Frequency outputs:

o

60 MHz (unmodulated)

o

2 x 48 MHz (unmodulated)

o

66.6 MHz (modulated): -1.7% down spread

Modulation rate: 30 KHz.

Supply voltage range: 3.3V ± 0.3V.

Available in 8-pin SOIC Package.

Commercial and Industrial Temperature range.

RoHS Compliant

Product Description

The ASM3P2111B is a versatile spread spectrum

frequency

modulator

that

reduces

electromagnetic

interference (EMI) at the clock source. The ASM3P2111B

allows significant system cost savings by reducing the

number of circuit board layers and shielding that are

required to pass EMI regulations. The ASM3P2111B

modulates the output of PLL in order to spread the

bandwidth of a synthesized clock, thereby decreasing 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

clock generators. Lowering EMI by increasing a signal’s

bandwidth is called spread spectrum clock generation.

Applications

ASM3P2111B is targeted towards EMI management for

high speed digital applications such as PC peripheral

devices, consumer electronics and embedded controller

systems.

Block Diagram

Crystal

Oscillator

66.6 MHz

Modulated

XIN /CLKIN

XOUT

48 MHz_2

60 MHz

48 MHz_1

PLL1

PLL2

48 MHz_1