參數(shù)資料
型號(hào): ICS841S012DKILFT
廠商: IDT, Integrated Device Technology Inc
文件頁(yè)數(shù): 4/23頁(yè)
文件大?。?/td> 0K
描述: IC FREQ SYNTHESIZER 56VFQFN
標(biāo)準(zhǔn)包裝: 1,000
系列: HiPerClockS™, PCI Express® (PCIe)
類型: 時(shí)鐘/頻率合成器,多路復(fù)用器
PLL:
主要目的: PCI Express(PCIe)
輸入: LVCMOS,LVTTL,晶體
輸出: HCSL,LVCMOS,LVTTL
電路數(shù): 1
比率 - 輸入:輸出: 2:12
差分 - 輸入:輸出: 是/無(wú)
頻率 - 最大: 250MHz
電源電壓: 3.135 V ~ 3.465 V
工作溫度: -40°C ~ 85°C
安裝類型: 表面貼裝
封裝/外殼: 56-VFQFN 裸露焊盤
供應(yīng)商設(shè)備封裝: 56-VFQFP-EP(8x8)
包裝: 帶卷 (TR)
ICS841S012BKI REVISION A NOVEMBER 10, 2009
12
2009 Integrated Device Technology, Inc.
ICS841S012I Data Sheet
CRYSTAL-TO-0.7V DIFFERENTIAL HCSL/LVCMOS FREQUENCY SYNTHESIZER
SPREAD SPECTRUM
Spread-spectrum clocking is a frequency modulation technique
for EMI reduction. When spread-spectrum is enabled, a 32kHz
triangle waveform is used with 0.6% down-spread (+0.0% / -
0.5%) from the nominal output frequency. An example of a tri-
angle frequency modulation profile is shown in
Figure 4A be-
low. The ramp profile can be expressed as:
Fnom = Nominal Clock Frequency in Spread OFF mode
Fm = Nominal Modulation Frequency (30kHz)
δ = Modulation Factor (0.6% down spread)
The ICS841S012BI triangle modulation frequency deviation
will not exceed 0.7% down-spread from the nominal clock fre-
quency (+0.0% / -0.5%). An example of the amount of down
spread relative to the nominal clock frequency can be seen in
the frequency domain, as shown in
Figure 4B. The ratio of this
width to the fundamental frequency is typically 0.4%, and will
not exceed 0.7%. The resulting spectral reduction will be greater
than 5dB, as shown in
Figure 4B. It is important to note the
ICS841S012DI 5dB minimum spectral reduction is the compo-
nent-specific EMI reduction, and will not necessarily be the
same as the system EMI reduction.
FIGURE 4B. 200MHZ CLOCK OUTPUT IN FREQUENCY DOMAIN
(A) SPREAD-SPECTRUM OFF (B) SPREAD-SPECTRUM ON
FIGURE 4A. TRIANGLE FREQUENCY MODULATION
(1 -
δ) fnom + 2 Fm x δ x Fnom x t when 0 < t <
,
(1 -
δ) fnom - 2 Fm x δ x Fnom x t when
< t <
1
2Fm
1
2Fm
1
Fm
1/fm
0.5/fm
Fnom
(1 -
δ) Fnom
Frequency
Time
BA
Δ 10 dBm
δ = .6%
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參數(shù)描述
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