November 2003

P2560B

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.

Features

FCC approved method of EMI attenuation

Generates a low EMI spread spectrum and a non-

spread reference signal of the input clock

frequency

Optimized for input frequency range from 20 to 32

MHz

Internal loop filter minimizes external components

and board space

Two selectable spread ranges

Low inherent cycle-to-cycle jitter

3.3 V or 5 V operating voltage

CMOS/TTL compatible inputs and outputs

Ultra low power CMOS design: 5.50 mA @3.3 V

Supports notebook VGA and other LCD timing

controller applications

SSON pin for Spread Spectrum On/Off and

Standby Mode controls

Available in 8-pin SOIC and TSSOP

Product Description

The P2560B is a versatile spread spectrum frequency

modulator designed specifically for a wide range of clock

frequencies. It reduces electromagnetic interference

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

of EMI of downstream clock and data dependent signals.

It allows significant system cost savings by reducing the

number of circuit board layers and shielding traditionally

required to pass EMI regulations.

The P2560B 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 P2560B uses the most efficient and optimized

modulation profile approved by the FCC and is

implemented by using a proprietary all-digital method.

Applications

The P2560B is targeted toward the notebook VGA chip

and other displays using an LVDS interface, PC

peripheral devices, and embedded systems

Block Diagram