Document
August 2005
www.DataSheet4U.com rev 2.1
ASM3P18S19B
Notebook LCD Panel EMI Reduction IC
Features
FCC approved method of EMI attenuation. Provides up to 15dB EMI reduction. Generates a low EMI Spread Spectrum clock and a non-spread reference clock of the input frequency. Optimized for Frequency range from 20 to 40MHz. Internal loop filter minimizes external components and board space. Low Inherent Cycle-to-Cycle jitter. Two spread % selections: -1.25% to -1.75%. 3.3V Operating Voltage. Low power CMOS design. Supports notebook VGA and other LCD timing controller applications. Power Down function for mobile application. Available in Commercial temperature range. Available in 8-pin SOIC and TSSOP Packages. RoHS Compliant
allows significant system cost savings by reducing the number of circuit board layers, ferrite beads, shielding, and other passive components that are traditionally required to pass EMI regulations. The ASM3P18S19B modulates the output of a single PLL in order to “spread” the bandwidth of a synthesized clock, and more importantly, decreases the peak amplitudes of its harmonics. This results in significantly lower system EMI compared to the typical narrow band signal produced by oscillators and most frequency generators. Lowering EMI by increasing a signal’s bandwidth is called ‘Spread Spectrum Clock Generation’. The ASM3P18S19B uses the most efficient and optimized modulation profile approved by the FCC and is implemented in a proprietary all digital method.
Applications
The ASM3P18S19B is targeted towards EMI management for memory and LVDS interfaces in mobile graphic chipsets and high-speed digital applications such as PC peripheral devices, consumer electronics, and embedded controller systems.
Product Description
The ASM3P18S19B is a Versatile Spread Spectrum Frequency Modulator designed specifically for input clock frequencies from 20 to 40MHz. (Refer Input Frequency and Modulation Rate Table). The ASM3P18S19B reduces electromagnetic interference (EMI) at the clock source, allowing system wide reduction of EMI of down stream clock and data dependent signals. The ASM3P18S19B
Block Diagram
PD#
SRS
VDD
Modulation XIN/CLKIN Crystal Oscillator Frequency Divider Feedback Divider
PLL
XOUT
Phase Detector
Loop Filter
VCO
Output Divider
REF
ModOUT
VSS
Alliance Semiconductor 2575 Augustine Drive • Santa Clara, CA • Tel: 408.855.4900 • Fax: 408.855.4999 • www.alsc.com
Notice: The information in this document is subject to change without notice.
August 2005 rev 2.1 www.DataSheet4U.com
Pin Configuration
XIN/ CLKIN VSS SRS ModOUT 1 2 3 4 8 7 6 5 XOUT VDD PD# REF
ASM3P18S19B
ASM3P18S19B
Pin Description Pin#
1 2 3 4 5 6 7 8
Pin Name
XIN / CLKIN VSS SRS ModOUT REF PD# VDD XOUT
Type
I P I O O I P O
Description
Crystal Connection or external frequency input.This pin has dual functions. It can be connected to either an external crystal or an external reference clock Ground Connection. Connect to.
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