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AD9512 参数 Datasheet PDF下载

AD9512图片预览
型号: AD9512
PDF下载: 下载PDF文件 查看货源
内容描述: 1.2 GHz的时钟分配IC , 1.6 GHz的输入,分频器,延迟调整,五路输出 [1.2 GHz Clock Distribution IC, 1.6 GHz Inputs, Dividers, Delay Adjust, Five Outputs]
分类和应用: 时钟
文件页数/大小: 48 页 / 1007 K
品牌: ABCO [ ABCO ELECTRONICS CO.LTD ]
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AD9512  
DIV = 18  
This path adds some jitter greater than that specified for the  
nondelay outputs. This means that the delay function should be  
used primarily for clocking digital chips, such as FPGA, ASIC,  
DUC, and DDC, rather than for data converters. The jitter is  
higher for long full scales (~10 ns). This is because the delay  
block uses a ramp and trip points to create the variable delay. A  
longer ramp means more noise might be introduced.  
Unique Phase Offsets Are Phase = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,  
11, 12, 13, 14, 15, 16, 17  
Phase offsets may be related to degrees by calculating the phase  
step for a particular divide ratio:  
Phase Step = 360°/(Divide Ratio) = 360°/DIV  
Using some of the same examples,  
DIV = 4  
Calculating the Delay  
The following values and equations are used to calculate the  
delay of the delay block.  
Value of Ramp Current Control Bits (Register 35h or Register 39h  
<2:0>) = Iramp_bits  
Phase Step = 360°/4 = 90°  
Unique Phase Offsets in Degrees Are Phase = 0°, 90°,  
180°, 270°  
I
RAMP (μA) = 200 × (Iramp_bits + 1)  
No. of Caps = No. of 0s + 1 in Ramp Control Capacitor  
(Register 35h or Register 39h <5:3>), that is, 101 = 1 + 1 = 2;  
110 = 2; 100 = 2 + 1 = 3; 001 = 2 + 1 = 3; 111 = 0 + 1 = 1)  
DIV = 7  
Phase Step = 360°/7 = 51.43°  
Delay_Range (ns) = 200 × [(No. of Caps + 3)/(IRAMP)] × 1.3286  
Unique Phase Offsets in Degrees Are Phase = 0°, 51.43°,  
102.86°, 154.29°, 205.71°, 257.15°, 308.57°  
No.of Caps 1⎞  
×104  
+
×6  
Offset  
(
ns  
)
= 0.34 +  
(
1600 IRAMP  
)
DELAY BLOCK  
IRAMP  
OUT4 (LVDS/CMOS) includes an analog delay element that  
can be programmed (Register 34h to Register 36h) to give  
variable time delays (ΔT) in the clock signal passing through  
that output.  
Delay_Full_Scale (ns) = Delay_Range + Offset  
Fine_Adj = Value of Delay Fine Adjust (Register 36h or  
Register 3Ah <5:1>), that is, 11111 = 31  
CLOCK INPUT  
OUT4 ONLY  
Delay (ns) = Offset + Delay_Range × Fine_adj × (1/31)  
OUTPUTS  
÷N  
SELECT  
The AD9512 offers three different output level choices:  
LVDS  
CMOS  
LVPECL, LVDS, and CMOS. OUT0 to OUT2 are LVPECL only.  
OUT3 and OUT4 can be selected as either LVDS or CMOS.  
Each output can be enabled or turned off as needed to save  
power.  
OUTPUT  
DRIVER  
ΔT  
FINE DELAY ADJUST  
(32 STEPS)  
FULL-SCALE: 1ns TO 10ns  
The simplified equivalent circuit of the LVPECL outputs is  
shown in Figure 27.  
Figure 26. Analog Delay (OUT4)  
The amount of delay that can be used is determined by the  
frequency of the clock being delayed. The amount of delay can  
approach one-half cycle of the clock period. For example, for a  
10 MHz clock, the delay can extend to the full 10 ns maximum  
of which the delay element is capable. However, for a 100 MHz  
clock (with 50ꢀ duty cycle), the maximum delay is less than  
5 ns (or half of the period).  
3.3V  
OUT  
OUTB  
OUT4 allows a full-scale delay in the range 1 ns to 10 ns. The  
full-scale delay is selected by choosing a combination of ramp  
current and the number of capacitors by writing the appropriate  
values into Register 35h. There are 32 fine delay settings for  
each full scale, set by Register 36h.  
GND  
Figure 27. LVPECL Output Simplified Equivalent Circuit  
Rev. A | Page 30 of 48