September 2005

P2040C

rev 1.4

LCD Panel EMI Reduction IC

3 of 9

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

Spread Spectrum Selection

Table 1 illustrates the possible spread spectrum options. The optimal setting should minimize system EMI to the fullest without

affecting system performance. The spreading is described as a percentage deviation of the center frequency

(Note: The center frequency is the frequency of the external reference input on CLKIN, Pin 1).

Example: P2040C is designed for high resolution flat panel applications and is able to support panel frequencies from 50MHz

to 170MHz. For a 65MHz pixel clock frequency, a spreading selection of MRA=0, SR1=1 and SR0 =1 provides a percentage

deviation of ±1.50% (see Table 1). This result in frequency on ModOUT being swept from 64.03MHz to 65.98MHz at a

modulation rate of 50.77KHz (see Table 1). This particular example (see Figure below) given here is a common EMI reduction

method for notebook LCD panel and has already been implemented by most of the leading OEM and mobile graphic

accelerator manufacturers.

Application Schematic for Mobile LCD Graphics Controllers

`

Modulated 65MHz signal with

±1.5 % deviation and modulation

rate of 50.77KHz. This signal is

connected back to the spread

spectrum input pin (SSIN) of the

graphics accelerator.

1

2

3

4

CLKIN

MRA

SR1

VSS

SR0

5

6

7

8

SSON#

ModOUT

VDD

65MHz from graphics accelerator

+3.3V

0.1µF

P2040C

Digital control for the SS enable

or disable