November 2006

P2040C

rev 1.6

LCD Panel EMI Reduction IC

3 of 9

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

1

2

3

4

CLKIN

MRA

SR1

VSS

SR0

5

6

7

8

SSON#

ModOUT

VDD

P2040C

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 173MHz. 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.

65MHz from graphics accelerator

+3.3V

0.1µF

Digital control for the SS enable

or disable