asm3x2105a Alliance Memory, Inc, asm3x2105a Datasheet - Page 3

• Manufacturer Part Number: asm3x2105a
• Description: Frequency Reduction
• Manufacturer: Alliance Memory, Inc

October 2003
rev 1.0
Spread Spectrum
Spreading the spectrum of the signal reduces the system EMI. 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).
Example:
The ASM3X2105A is designed for communications, digital video and imaging applications. It is not only
optimized for operation in the 6MHz – 12MHz range, but its output frequency can be extended down to one half
of the input clock frequency using the divide-by-two feature. This feature extends low frequency operation to as
low as 3MHz. Setting pin 3 low (DIV2=0; divide-by-two mode) sets the output frequency (MODOUT) to half the
frequency of the input clock (CLKIN). This is a simple way to generate a spread spectrum modulated low
frequency clock when only a higher frequency signal is available. If you want the output frequency to be the
same as the input, you can either set DIV2=1 or leave it unconnected.
8.832MHz Crystal
Notice: The information in this document is subject to change without notice.
Low Frequency EMI Reduction
3
1
2
4
CLKIN
XOUT
DIV2
VSS
ASM3X2105A
MODOUT
SSON#
VDD
SR0
7
5
8
6
0.1µF
+5V
ASM3X2105A
Modulated 4.416MHz
is connected to CLK
input pin of the system
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