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CS2000P-CZZR 参数 Datasheet PDF下载

CS2000P-CZZR图片预览
型号: CS2000P-CZZR
PDF下载: 下载PDF文件 查看货源
内容描述: 小数N分频时钟合成器与时钟乘法器 [Fractional-N Clock Synthesizer & Clock Multiplier]
分类和应用: 时钟
文件页数/大小: 30 页 / 568 K
品牌: CIRRUS [ CIRRUS LOGIC ]
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CS2000-OTP  
It is important to note that Auto R-Mod (if enabled) is applied in addition to any R-Mod already selected  
by the RModSel[1:0] modal parameter and is used to calculate the Effective Ratio (see Section 5.4.5 on  
page 16).  
Auto R-Mod can be used to generate the appropriate oversampling clock (MCLK) for audio A/D and D/A  
converters. For example, if the clock applied to CLK_IN is the audio sample rate, Fs (also known as the  
word, frame or Left/Right clock), and SysClk is 12.288 MHz (REF_CLK = 12.288 MHz with RefClkDiv[1:0]  
set to ‘10’), FsDetect[1:0] would then reflect the frequency range of the audio sample rate. An R of 512  
UD  
generates the audio oversampling clocks as shown in Table 4.  
Inferred Audio Sample Rate Speed Mode (used for Audio Oversampling  
FsDetect[1:0]  
when SysClk = 12.288 MHz  
audio converters)  
Clock  
512 x  
256 x  
128 x  
00  
01  
10  
< 54.8 kHz  
Single Speed  
54.8 kHz to 128 kHz  
> 128 kHz  
Double Speed  
Quad Speed  
Table 4. Example Audio Oversampling Clock Generation from CLK_IN  
Referenced Control  
Parameter Definition  
Ratio 0-3................................“Ratio 0 - 3” on page 24  
RModSel[1:0] ........................“R-Mod Selection (RModSel[1:0])” section on page 23  
AutoRMod .............................“Auto R-Modifier Enable (AutoRMod)” on page 24  
M2Config[2:0]........................“M2 Pin Configuration (M2Config[2:0])” on page 26  
5.4.5  
Effective Ratio (R  
)
EFF  
The Effective Ratio (R  
) is an internal calculation comprised of R and the appropriate modifiers, as  
EFF  
UD  
previously described. R  
is calculated as follows:  
EFF  
Frequency Synthesizer (Static Ratio) Mode: R  
= RUD R-Mod  
EFF  
Hybrid PLL (Dynamic Ratio) Mode: R  
= RUD R-Mod Auto R-Mod  
EFF  
To simplify operation the device handles some of the ratio calculation functions automatically (such as  
when the internal timing reference clock divider is set). For this reason, the Effective Ratio does not need  
to be altered to account for internal dividers.  
Ratio modifiers which would produce an overflow or truncation of R  
should not be used. In all cases,  
EFF  
the maximum and minimum allowable values for R  
are dictated by the frequency limits for both the  
EFF  
input and output clocks as shown in the “AC Electrical Characteristics” on page 7.  
Selection of the user defined ratio from the four stored ratios is made by using the M[1:0] pins unless auto  
clock switching is enabled in which case the LockClk[1:0] modal parameter also selects the ratio (see  
“Fractional-N Source Selection” on page 16).  
Referenced Control  
Parameter Definition  
M[1:0] pins.............................“M1 and M0 Mode Pin Functionality” on page 20  
LockClk[1:0] ..........................“Lock Clock Ratio (LockClk[1:0])” section on page 24  
5.4.6  
Fractional-N Source Selection  
To select between the static ratio based Frequency Synthesizer Mode and the dynamic ratio based Hybrid  
PLL Mode, the source for the fractional-N value for the Frequency Synthesizer must be changed. The  
Fractional-N value can either be sourced directly from the Effective Ratio (static ratio) or from the output  
of the Digital PLL (dynamic ratio) (see Figure 12 on page 18). The setting of this function can be made  
manual or automatically depending on the presence of CLK_IN.  
16  
DS758PP1  
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