參數(shù)資料
型號(hào)： ICS1531
英文描述： Triple 8-bit MSPS A/D Converters with Line-Locked Clock Generator
中文描述： 三8位MSPS的的A / D轉(zhuǎn)換器與電源同步時(shí)鐘發(fā)生器
文件頁(yè)數(shù)： 56/76頁(yè)
文件大?。?/td> 529K
代理商： ICS1531
ICS1531 Rev N 12/1/99
December, 1999
56
Chapter 7
Programming
ICS1531 Data Sheet - Preliminary
Copyright 1999, Integrated Circuit Systems, Inc.
All rights reserved.
7.3
Programming Spread Spectrum
7.3.1
Spread Spectrum Definition and Purpose
Spread spectrum is a process for distributing (or ‘spreading’) the energy of a single-frequency signal over a
wider frequency spectrum so that it reduces the peak radiated energy on any single frequency.
The need for spread-spectrum technology results from the increase in speeds of PCs and the subsequent
increase in operating resolutions. That is, there has been an increase both in the speed of (1) pixel clocks
for cathode-ray tube displays and (2) panel clocks for LCD displays.
Accompanying these increases has been an increase in generated electro-magnetic interference (EMI). In
some cases, EMI emissions of the fundamental frequency can be too high to pass a country’s
communications regulations [such as those from the American government agency, the Federal
Communications Commission (FCC)].
Figure 7-3
shows an idealized (1) unmodulated carrier signal and (2) modulated signal resulting from
spread-spectrum technology. (Both of the actual signals have a fundamental frequency and more variable
peaks and sidebands than what this figure shows.)
1.
In this example, the unmodulated carrier signal has a frequency whose peak amplitude creates EMI
emissions that are too high to pass FCC requirements.
To reduce EMI, the ICS1531 use spread-spectrum technology to modulate the carrier frequency of the
input timing signals from either the memory clock, or the panel clock, or both.
Figure 7-3
shows how the
energy of the unmodulated signal can be redistributed as sidebands of a modulated signal.
The peak amplitude of the composite single-frequency carrier signal is thereby attenuated. As a result,
the EMI peak decreases, while the total signal energy is maintained. This attenuation occurs without
increasing cycle-to-cycle jitter. Consequently, system design costs can be reduced by decreasing the
need to design shielding for the ICS1531.
2.
Note:
Both the MCLK and PNLCLK PLLs use spread-spectrum technology. (The pixel PLL does not.) For
information on how to achieve specific spread-spectrum results, see ICS1531 application notes.
Figure 7-3.
Signal Characteristics (1) Before and (2) After Applying Spread-Spectrum Circuitry
Relative
Amplitude
(dB)
Clock Frequency (MHz)
6
9
1. Unmodulated Carrier Signal
(Narrow Bandwidth)
Spread Spectrum
2. Modulated Carrier Signal
(Increased Bandwidth: Spectrum of
sideband signals has spread.)
3
0
Note:
Figure shows idealized signals.
(Details are not shown.)
相關(guān)PDF資料
PDF描述
ICS1560M-001 Video/Graphics Clock Generator
ICS1560M-003 Video/Graphics Clock Generator
ICS1560N-001 Video/Graphics Clock Generator
ICS1560N-003 Video/Graphics Clock Generator
ICS1561AM-706 Video/Graphics Clock Generator
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
ICS1532 制造商:IDT 制造商全稱:Integrated Device Technology 功能描述:110 MHZ TRIPLE 8-BIT ADC WITH CLOCK GENERATOR
ICS1560M-001 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Video/Graphics Clock Generator
ICS1560M-003 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Video/Graphics Clock Generator
ICS1560N-001 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Video/Graphics Clock Generator
ICS1560N-003 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Video/Graphics Clock Generator
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