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参数资料
| 型号： | W134M |
| 厂商： | CYPRESS SEMICONDUCTOR CORP |
| 元件分类： | XO, clock |
| 英文描述： | Direct Rambus Clock Generator |
| 中文描述： | PROC SPECIFIC CLOCK GENERATOR, PDSO24 |
| 封装： | 0.150 INCH, SSOP-24 |
| 文件页数： | 4/10页 |
| 文件大小： | 244K |
| 代理商： | W134M |
W137
4
Spread Spectrum Clocking
The device generates a clock that is frequency modulated in
order to increase the bandwidth that it occupies. By increasing
the bandwidth of the fundamental and its harmonics, the am-
plitudes of the radiated electromagnetic emissions are re-
duced. This effect is depicted in
Figure 3
.
As shown in
Figure 3
, a harmonic of a modulated clock has a
much lower amplitude than that of an unmodulated signal. The
reduction in amplitude is dependent on the harmonic number
and the frequency deviation or spread. The equation for the
reduction is
dB = 6.5 + 9*log
10
(P) + 9*log
10
(F)
Where
P
is the percentage of deviation and
F
is the frequency
in MHz where the reduction is measured.
The output clock is modulated with a waveform depicted in
Figure 4
. This waveform, as discussed in “Spread Spectrum
Clock Generation for the Reduction of Radiated Emissions” by
Bush, Fessler, and Hardin, produces the maximum reduction
in the amplitude of radiated electromagnetic emissions. The
deviation selected for this chip is –0.5% of the selected fre-
quency.
Figure 4
details the Cypress spreading pattern.
Cypress does offer options with more spread and greater EMI
reduction. Contact your local Sales representative for details
on these devices.
Spread Spectrum clocking is activated or deactivated through
I/O pin #26.
Spread
Spectrum
Enabled
EMI Reduction
Non-
Spectrum
Figure 3. Clock Harmonic with and without SSCG Modulation Frequency Domain Representation
MAX
MIN
1
2
3
4
5
6
7
8
9
1
1
2
3
4
5
6
7
8
9
1
F
Figure 4. Typical Modulation Profile
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相关代理商/技术参数 |
参数描述 |
|---|---|
| W134M_05 | 制造商:CYPRESS 制造商全称:Cypress Semiconductor 功能描述:Direct Rambus⑩ Clock Generator |
| W134MH | 功能描述:时钟发生器及支持产品 Direct Rambus ClkGen 400MHz Diff Out RoHS:否 制造商:Silicon Labs 类型:Clock Generators 最大输入频率:14.318 MHz 最大输出频率:166 MHz 输出端数量:16 占空比 - 最大:55 % 工作电源电压:3.3 V 工作电源电流:1 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:QFN-56 |
| W134MHT | 功能描述:时钟发生器及支持产品 Direct Rambus ClkGen 400MHz Diff Out RoHS:否 制造商:Silicon Labs 类型:Clock Generators 最大输入频率:14.318 MHz 最大输出频率:166 MHz 输出端数量:16 占空比 - 最大:55 % 工作电源电压:3.3 V 工作电源电流:1 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:QFN-56 |
| W134MIP-1 | 制造商:Magnecraft 功能描述: |
| W134MIP-2 | 制造商:Magnecraft 功能描述: |
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