October 2003
rev 1.0
Spread Spectrum Selection
P2040A
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, P2040A 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 MRA=0, SR1=1 and
SR0=0 provides a percentage deviation of ±0.75% from F
IN
. This results in the frequency on ModOUT being
swept from 64.51 to 65.49MHz at a modulation rate of 56.24KHz.
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
65MHz from graphics accelerator
1
CLKIN
MRA
SR1
VSS
VDD
SR0
ModOUT
SSON#
8
2
7
0.1µF
Modulated 65MHz signal with
±0.75 deviation and modulation
rate of 56.24KHz. This signal is
connected back to the spread
+3.3V
spectrum input pin (SSIN) of the
graphics accelerator.
3
6
4
5
P2040A
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 ]
