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參數(shù)資料
| 型號： | MPC930FA |
| 廠商： | FREESCALE SEMICONDUCTOR INC |
| 元件分類： | 時鐘產(chǎn)生/分配 |
| 英文描述： | 140 MHz, PROC SPECIFIC CLOCK GENERATOR, PQFP32 |
| 封裝： | TQFP-32 |
| 文件頁數(shù)： | 3/12頁 |
| 文件大?。?/td> | 326K |
| 代理商： | MPC930FA |
MPC930 MPC931
MOTOROLA ADVANCED CLOCK DRIVERS DEVICE DATA
59
Figure 15. PLL Block Diagram
fref
Phase
Detector
Qn
VCO
LPF
÷P
÷N
÷m
N fref +
fQn N P
m
fref +
fVCO
m
,fVCO + fQn N P
m = 8
P = 1 (Power_Dn=‘0’), 2 (Power_Dn=‘1’)
For the MPC930 clock driver, the following will provide an
example of how to determine the crystal frequency required for
a given design.
Given:
Qa
= 66.6MHz
Qb
= 33.3MHz
Qc
= 22.2MHz
Power_Dn = ‘0’
fref +
fQn N P
m
From Table 4
fQc = VCO/6 then N = 6
From Figure 15
m = 8 and P = 1
fref +
22.22 6 1
8
+ 16.66MHz
Driving Transmission Lines
The MPC930/931 clock driver was designed to drive high
speed signals in a terminated transmission line environment.
To provide the optimum flexibility to the user the output drivers
were designed to exhibit the lowest impedance possible. With
an output impedance of less than 10
the drivers can drive
either parallel or series terminated transmission lines. For
more information on transmission lines the reader is referred to
application note AN1091 in the Timing Solutions data book
(DL207/D).
In most high performance clock networks point–to–point
distribution of signals is the method of choice. In a point–to–
point scheme either series terminated or parallel terminated
transmission lines can be used. The parallel technique termi-
nates the signal at the end of the line with a 50
resistance to
VCC/2. This technique draws a fairly high level of DC current
and thus only a single terminated line can be driven by each
output of the MPC930/931 clock driver. For the series termi-
nated case however there is no DC current draw, thus the out-
puts can drive multiple series terminated lines. Figure 16 illus-
trates an output driving a single series terminated line vs two
series terminated lines in parallel. When taken to its extreme
the fanout of the MPC930/931 clock driver is effectively
doubled due to its capability to drive multiple lines.
Figure 16. Single versus Dual Transmission Lines
7
IN
MPC930/931
OUTPUT
BUFFER
RS = 43
ZO = 50
OutA
7
IN
MPC930/931
OUTPUT
BUFFER
RS = 43
ZO = 50
OutB0
RS = 43
ZO = 50
OutB1
The waveform plots of Figure 17 show the simulation re-
sults of an output driving a single line vs two lines. In both
cases the drive capability of the MPC930/931 output buffers is
more than sufficient to drive 50
transmission lines on the inci-
dent edge. Note from the delay measurements in the simula-
tions a delta of only 43ps exists between the two differently
loaded outputs. This suggests that the dual line driving need
not be used exclusively to maintain the tight output–to–output
skew of the MPC930/931. The output waveform in Figure 17
shows a step in the waveform, this step is caused by the im-
pedance mismatch seen looking into the driver. The parallel
combination of the 43
series resistor plus the output imped-
ance does not match the parallel combination of the line im-
pedances. The voltage wave launched down the two lines will
equal:
VL = VS ( Zo / (Rs + Ro +Zo))
Zo = 50
|| 50
Rs = 43
|| 43
Ro = 7
VL = 3.0 (25 / (21.5 + 7 + 25) = 3.0 (25 / 53.5)
= 1.40V
At the load end the voltage will double, due to the near unity
reflection coefficient, to 2.8V. It will then increment towards the
quiescent 3.0V in steps separated by one round trip delay (in
this case 4.0ns).
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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| MPC931 | 制造商:Motorola Inc 功能描述: |
| MPC9315 | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:2.5V and 3.3V CMOS PLL Clock Generator and Driver |
| MPC9315AC | 功能描述:鎖相環(huán) - PLL 2.5 3.3V 160MHz Clock Generator RoHS:否 制造商:Silicon Labs 類型:PLL Clock Multiplier 電路數(shù)量:1 最大輸入頻率:710 MHz 最小輸入頻率:0.002 MHz 輸出頻率范圍:0.002 MHz to 808 MHz 電源電壓-最大:3.63 V 電源電壓-最小:1.71 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:QFN-36 封裝:Tray |
| MPC9315ACR2 | 功能描述:時鐘發(fā)生器及支持產(chǎn)品 FSL 1-8 LVCMOS PLL Clock Generator RoHS:否 制造商:Silicon Labs 類型:Clock Generators 最大輸入頻率:14.318 MHz 最大輸出頻率:166 MHz 輸出端數(shù)量:16 占空比 - 最大:55 % 工作電源電壓:3.3 V 工作電源電流:1 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-56 |
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