September 2003

ASM3P2811A/B

ASM3P2812A/B

ASM3P2814A/B

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 Power EMI Reduction IC

Features

FCC approved method of EMI attenuation.

Provides up to 15dB EMI reduction.

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

spectrum clock of the input frequency.

o

1X: ASM3P2811A/B

o

2X: ASM3P2812A/B

o

4X: ASM3P2814A/B

Optimized for input frequency range from 10MHz

to 40 MHz.

o

ASM3P2811A/B: 10 to 40MHz

o

ASM3P2812A/B: 10 to 40MHz

o

ASM3P2814A/B: 10 to 40MHz

Internal loop filter minimizes external components

and board space.

Selectable spread options: Down Spread and

Center Spread.

8 spread frequency deviation selections:

o

±0.625% to –3.5%

Low inherent cycle-to-cycle jitter.

3.3V operating voltage range.

CMOS/TTL compatible inputs and outputs.

Pinout

compatible

with

Cypress

CY25811,

CY25812 and CY25814.

Products are available for industrial temperature

range.

Available in 8-pin SOIC and TSSOP.

Product Description

The ASM3P28XX devices are versatile spread spectrum

frequency modulators designed specifically for a wide

range of input clock frequencies from 10MHz to 40MHz.

(Refer Input/Output Frequency Range Selection Table).

The ASM3P28XX can generate an EMI reduced clock

from

crystal, ceramic resonator, or system clock. The

ASM3P28XX-A and the ASM3P28XX-B offer various

combinations

of

spread

options

and

percentage

deviations

(Refer

Output

Frequency

Deviation

and

Spread Option Selection Table). These combinations

include Down and Center Spread and percentage

deviation range from ±0.625% to –3.50%.

The ASM3P28XX reduces electromagnetic interference

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

of EMI of

down stream clock and data dependent

signals. The ASM3P28XX 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 ASM3P28XX 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’.

The ASM3P28XX uses the most efficient and optimized

modulation

profile

approved

by

the

FCC

and

is

implemented in a proprietary all-digital method.

Applications

The ASM3P28XX is targeted towards EMI management

for memory and LVDS interfaces in mobile graphic

chipsets and high-speed digital applications such as PC

peripheral devices, consumer electronics, and embedded

controller systems.