October 2003

ASM3P2109A

rev 0.3

PRELIMINARY INFORMATION

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 4X REF EMI spread output



Spectrum clock of the input frequency.



Optimized for input frequency range from

10 to 20MHz.



External Loop Filter for configurability and

flexibility in application and design (spread

percentage adjust)



Reference Output



Power Down Mode



Very Low Cycle-to-Cycle Jitter.



3.3V operating Range



CMOS / TTL compatible inputs and outputs



Available in 8-pin SOIC and 8-pin TSSOP

packages.

Product Description

The ASM3P2109A device is a versatile spread spectrum

Frequency Synthesizer / Modulator designed specifically

for a wide Range of input clock frequencies from 10MHz to

20MHz with a 4X multiplier for output clock frequencies

from 40MHz to 80 MHz.

The ASM3P2109A generates an EMI reduced clock signal

from a crystal, ceramic resonator, or system clock.

The

ASM3P2109A generates a range of modulation rates and

deviations (spread) from Center Frequency based upon the

input frequency, and is set / determined via an external

filter network ( see Loop Filter Selection table )

The ASM3P2109A reduces Electro Magnetic Interference

(EMI), at the Clock Source, allowing system wide reduction

of EMI on downstream clock and data dependant signals.

The resulting EMI reduction provides for significant cost

savings by reducing the number of circuit board layers and

shielding that are traditionally associated with designs in

order to achieve EMI regulatory compliance.

The ASM3P2109A modulates the output of a single

PLL in order to “spread” the bandwidth of a

synthesized clock, thereby decreasing the Peak

amplitudes of its associated harmonics. This results

in significantly lower radiated EMI compared to the

narrow band signal produced by standard oscillators

and most clock synthesizers & generators. This

technique of lowering EMI by increasing the signals

bandwidth is called Spread Spectrum Clocking

(SSC). The ASM3P2109A utilizes the most efficient

and optimized modulation profile approved by the

FCC, and is implemented using a proprietary, All-

Digital method.

Applications

The ASM3P2109A is targeted towards the Consumer

and PC/Data Processing, or Computation markets.

Entertainment devices, LCD displays, Notebook

computers, PC peripheral devices, embedded

systems, PDA’s, and hand held devices provide a

platform to take full advantage of the feature set of

the ASM3P2109A.