August 2007
rev 1.5
Spread Spectrum Selection
P2042A
The
Modulation Selection Table
defines 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, pin1).
For example, P2042A is designed for high-resolution, flat panel applications and is able to support an XGA (1024 x 768) flat
panel operating at 65MHz (FIN) clock speed. A spreading selection of CP0=0, CP1=1 and SR0=0 provides a percentage
deviation of ±1.00% from F
IN
. This results in the frequency on ModOUT being swept from 65.65 to 64.35MHz at a modulation
rate of 101.54KHz.
Refer Modulation Selection Table.
The example in the following illustration is a common EMI reduction
method for a 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
+3.3V
65MHz from graphics accelerator
1 CLKIN
2 CP0
3 CP1
4 VSS
VDD
SR0
8
7
0.1µF
ModOUT 6
SSON# 5
Modulated 65MHz signal with
±1.00% deviation and
modulation rate of 101.54KHz.
This signal is connected back to
the spread spectrum input pin
(SSIN) of the graphics
accelerator.
P2042A
Digital control for the SS enable
or disable
LCD Panel EMI Reduction IC
Notice: The information in this document is subject to change without notice.
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PULSECORE [ PulseCore Semiconductor ]
