Alliance Semiconductor

2595, Augustine Drive

• Santa Clara • CA 95054 • Tel 408 855 4900 • Fax 408 855 4999 • www.alsc.com

November 2003

ASM3P2190A

rev 1.0

Notice: The information in this document is subject to change without notice.

Peak Reducing EMI Solution

Features

signal at the output.

output.

TSSOP packages.

Product Description

The ASM3P2190A is a versatile spread spectrum

frequency modulator designed specifically for a

wide

range

of

clock

frequencies.

The

ASM3P2190A

reduces

electromagnetic

interference (EMI) at the clock source, allowing

system wide reduction of EMI of down stream

clock

and

data

dependent

signals.

The

ASM3P2190A allows significant system cost

savings by reducing the number of circuit board

layers and shielding that are traditionally required

to pass EMI regulations.

The ASM3P2190A modulates the output of a

single 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.

The ASM3P2190A uses the most efficient and

optimized modulation profile approved by the

FCC and is implemented by using a proprietary

all-digital method.

Applications

The ASM3P2190A is targeted towards notebook

LCD displays, other displays using an LVDS

interface, PC peripheral devices and embedded

systems.

Key Specifications

Description

Specification

Supply voltages

Frequency range

6 MHz

≤ 30 MHz

Cycle-to-cycle jitter

325 ps (typical)

Selectable spread percentage

-1.25% or –2.4%

Output duty cycle

40/60% (worst case)

Output rise and fall time

5ns (maximum)

Simplified Block Diagram

Pin Diagram

X1

X2

3.3V

Spread spectrum output

(EMI suppressed)

CLKOUT

NC

VDD

FS1

1

2

3

4

5

6

7

8

CLKIN / X1

NC / X2

GND

SS%

ASM3P2190A