October 2003

P1817A/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 Mobile VGA EMI Reduction IC

Features

FCC approved method of EMI attenuation.

Generates a low EMI spread spectrum clock of the

input frequency.

Optimized for frequency range from:

o

P1817A – 20 to 30MHz. Operation

o

P1817B – 10 to 20MHz Operation

Internal loop filter minimizes external components

and board space.

Two selectable spread ranges.

Low inherent cycle-to-cycle jitter.

3.3V or 5V operating voltage range.

TTL or CMOS compatible outputs.

Ultra-low power CMOS design.

3.17mA @3.3V, 10MHz | 6.20mA@5.0V, 10MHz

4.28mA @3.3V, 14MHz | 7.50mA @5.0V, 14MHz

5.50mA @3.3V, 20MHz | 9.50mA @5.0V, 20MHz

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 P1817 is a versatile spread spectrum frequency

modulator designed specifically for input clock frequencies.

The P1817 reduces electromagnetic interference (EMI) at

the clock source, allowing system wide reduction of EMI of

down stream clock and data dependent signals. The P1817

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 P1817 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 P1817 uses the most efficient and optimized

modulation profile approved by the FCC and is

implemented in a proprietary all digital method.

Applications

The P1817 is targeted towards notebook VGA chip and

other displays using an LVDS interface, PC peripheral

devices, and embedded systems.

Block Diagram

VSS

XIN

XOUT

Crystal

Oscillator

Frequency

Divider

Feedback

Divider

Modulation

Phase

Detector

Loop

Filter

VCO

Output

Divider

ModOUT

PLL

VDD

SSON

SR0

Ref