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| 型号： | MPC93R51FA |
| 厂商： | FREESCALE SEMICONDUCTOR INC |
| 元件分类： | 时钟及定时 |
| 英文描述： | 93R SERIES, PLL BASED CLOCK DRIVER, 9 TRUE OUTPUT(S), 0 INVERTED OUTPUT(S), PQFP32 |
| 封装： | 7 X 7 MM, LQFP-32 |
| 文件页数： | 11/12页 |
| 文件大小： | 339K |
| 代理商： | MPC93R51FA |
Advanced Clock Drivers Devices
8
Freescale Semiconductor
MPC93R51
Figure 6. VCCA Power Supply Filter
As the noise frequency crosses the series resonant point
of an individual capacitor, its overall impedance begins to
look inductive, and thus, increases with increasing frequency.
The parallel capacitor combination shown ensures that a low
impedance path to ground exists for frequencies well above
the bandwidth of the PLL. Although the MPC93R51 has
several design features to minimize the susceptibility to
power supply noise (isolated power and grounds and fully
differential PLL), there still may be applications in which
overall performance is being degraded due to system power
supply noise. The power supply filter schemes discussed in
this section should be adequate to eliminate power supply
noise related problems in most designs.
Driving Transmission Lines
The MPC93R51 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 Freescale 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 MPC93R51 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 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 MPC93R51 clock
driver is effectively doubled due to its capability to drive
multiple lines.
Figure 7. Single versus Dual Transmission Lines
The waveform plots in Figure 8 show the simulation results
of an output driving a single line versus two lines. In both
cases, the drive capability of the MPC93R51 output buffer is
more than sufficient to drive 50
transmission lines on the
incident edge. Note from the delay measurements in the
simulations, a delta of only 43 ps 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 MPC93R51. The output
waveform in Figure 8 shows a step in the waveform. This
step is caused by the impedance mismatch seen looking into
the driver. The parallel combination of the 36
series
resistor, plus the output impedance, does not match the
parallel combination of the line impedances. The voltage
wave launched down the two lines will equal:
VL =VS (Z0 ÷ (RS+R0 +Z0))
Z0 = 50 || 50
RS = 36 || 36
R0 =14
VL = 3.0 (25 ÷ (18+17+25)
=1.31 V
At the load end the voltage will double, due to the near
unity reflection coefficient, to 2.6 V. It will then increment
towards the quiescent 3.0 V in steps separated by one round
trip delay (in this case 4.0 ns).
VCCA
VCC
MPC93R51
0.1
F
22 pF
0.1
F
RF
VCC
14
IN
MPC93R51
OUTPUT
BUFFER
RS = 36
ZO = 50
OutA
14
IN
MPC93R51
OUTPUT
BUFFER
RS = 36
ZO = 50
OutB0
RS = 36
ZO = 50
OutB1
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相关代理商/技术参数 |
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| MPC93R51FAR2 | 制造商:Integrated Device Technology Inc 功能描述:PLL CLOCK DRVR SGL 32LQFP - Tape and Reel |
| MPC93R52 | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:LOW VOLTAGE 3.3V LVCMOS 1:11 CLOCK GENERATOR |
| MPC93R52AC | 功能描述:时钟发生器及支持产品 FSL 1-11 LVCMOS PLL Clock Generator, pwr RoHS:否 制造商:Silicon Labs 类型:Clock Generators 最大输入频率:14.318 MHz 最大输出频率:166 MHz 输出端数量:16 占空比 - 最大:55 % 工作电源电压:3.3 V 工作电源电流:1 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:QFN-56 |
| MPC93R52ACR2 | 功能描述:时钟发生器及支持产品 FSL 1-11 LVCMOS PLL Clock Generator, pwr RoHS:否 制造商:Silicon Labs 类型:Clock Generators 最大输入频率:14.318 MHz 最大输出频率:166 MHz 输出端数量:16 占空比 - 最大:55 % 工作电源电压:3.3 V 工作电源电流:1 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:QFN-56 |
| MPC93R52FA | 功能描述:时钟发生器及支持产品 3.3V 240MHz Clock Generator RoHS:否 制造商:Silicon Labs 类型:Clock Generators 最大输入频率:14.318 MHz 最大输出频率:166 MHz 输出端数量:16 占空比 - 最大:55 % 工作电源电压:3.3 V 工作电源电流:1 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:QFN-56 |
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