ASM3P2180A

Peak Reducing EMI Solution

©2010 SCILLC. All rights reserved.

Publication Order Number:

JANUARY 2010 – Rev. 2

ASM3P2180/D

Features

• Generates a 1x EMI optimized clock output.

• Input frequency: 6MHz - 10MHz

18MHz - 30MHz

• Output frequency: 6MHz - 10MHz

18MHz - 30MHz

• Two selectable down spread options.

• Selectable frequency range.

• Integrated loop filter components.

• Operates with a 3.3V supply.

• CMOS design.

Product Description

The ASM3P2180A is a versatile spread spectrum

frequency modulator designed specifically for a wide

range of clock frequencies. ASM3P2180A reduces

electromagnetic interference (EMI) at the clock source,

allowing system wide reduction of EMI of down stream

clock and data dependent signals. ASM3P2180A allows

significant system cost savings by reducing the number

of circuit board layers, and shielding that are traditionally

required

to

pass

EMI

regulations.

ASM3P2180A

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. ASM3P2180A uses the most efficient and

optimized modulation profile approved by the FCC and

is implemented by using a proprietary all-digital method.

Applications

The ASM3P2180A is targeted towards notebook LCD

displays, other displays using an LVDS interface, PC

peripheral devices and embedded systems.

Block Diagram

PLL

Crystal

Oscillator

CLKIN / XIN

XOUT

CLKOUT

VDD

GND

SS%

FS

Modulation