參數(shù)資料
型號(hào): MPC9774
廠商: Motorola, Inc.
英文描述: 3.3V / 2,5V 1:14 LVCMOS PLL CLOCK GENERATOR
中文描述: 3.3 / 2,5 V 13:14:00的LVCMOS PLL時(shí)鐘發(fā)生器
文件頁(yè)數(shù): 9/16頁(yè)
文件大?。?/td> 217K
代理商: MPC9774
MPC9774
TIMING SOLUTIONS
9
MOTOROLA
Using the MPC9774 in zero-delay applications
Nested clock trees are typical applications for the
MPC9774. Designs using the MPC9774 as LVCMOS PLL
fanout buffer with zero insertion delay will show significantly
lower clock skew than clock distributions developed from
CMOS fanout buffers. The external feedback of the
MPC9774 clock driver allows for its use as a zero delay
buffer. The PLL aligns the feedback clock output edge with
the clock input reference edge resulting a near zero delay
through the device (the propagation delay through the device
is virtually eliminated). The maximum insertion delay of the
device in zero-delay applications is measured between the
reference clock input and any output. This effective delay
consists of the static phase offset, I/O jitter (phase or
long-term jitter), feedback path delay and the
output-to-output skew error relative to the feedback output.
Calculation of part-to-part skew
The MPC9774 zero delay buffer supports applications
where critical clock signal timing can be maintained across
several devices. If the reference clock inputs of two or more
MPC9774 are connected together, the maximum overall
timing uncertainty from the common CCLK input to any
output is:
tSK(PP) = t(
) + tSK(O) + tPD, LINE(FB) + tJIT(
) CF
This maximum timing uncertainty consist of 4
components: static phase offset, output skew, feedback
board trace delay and I/O (phase) jitter:
Figure 5. MPC9774 max. device-to-device skew
tPD,LINE(FB)
tJIT(
)
±
t
SK(O)
–t(
)
+t(
)
tJIT(
)
±
t
SK(O)
tSK(PP)
Max. skew
CCLKCommon
QFBDevice 1
Any QDevice 1
QFBDevice2
Any QDevice 2
Due to the statistical nature of I/O jitter a rms value (1
σ
) is
specified. I/O jitter numbers for other confidence factors (CF)
can be derived from
Table 12
.
Table 12. MPC9774 Divider
CF
Probability of clock edge within the distribution
±
1
±
2
±
3
±
4
±
5
±
6
0.68268948
0.95449988
0.99730007
0.99993663
0.99999943
0.99999999
The feedback trace delay is determined by the board
layout and can be used to fine-tune the effective delay
through each device. In the following example calculation a
I/O jitter confidence factor of 99.7% (
±
3
σ
) is assumed,
resulting in a worst case timing uncertainty from input to any
output of -495 ps to 495
ps2 rel
ative to CCLK:
tSK(PP) =
[–300ps...300ps] + [–150ps...150ps] +
[(15ps –3)...(15ps 3)] + tPD, LINE(FB)
tSK(PP) =
[–495ps...495ps] + tPD, LINE(FB)
Due to the frequency dependence of the I/O jitter, Figure 6
can be used for a more precise timing performance analysis.
Figure 6.
TBD.
See MPC961C application section for an ex-
ample I/O jitter characteristic
2. Final skew data pending specification
Driving Transmission Lines
The MPC9774 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 20
the
drivers can drive either parallel or series terminated
transmission lines. For more information on transmission
lines the reader is referred to Motorola application note
AN1091. 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 terminates 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 MPC9774 clock driver. For the series
terminated case however there is no DC current draw, thus
the outputs can drive multiple series terminated lines.
Figure 7 “Single versus Dual Transmission Lines” illustrates
an output driving a single series terminated line versus two
series terminated lines in parallel. When taken to its extreme
the fanout of the MPC9774 clock driver is effectively doubled
due to its capability to drive multiple lines.
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MPC9774FA 功能描述:鎖相環(huán) - PLL 3.3V 125MHz 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
MPC9774FAR2 功能描述:時(shí)鐘發(fā)生器及支持產(chǎn)品 FSL 1-14 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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