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| 型号： | MPC9239AC |
| 厂商： | IDT, Integrated Device Technology Inc |
| 文件页数： | 10/10页 |
| 文件大小： | 0K |
| 描述： | IC CLK SYNTH LV PECL 32-LQFP |
| 标准包装： | 250 |
| 类型： | 时钟/频率合成器 |
| PLL： | 是 |
| 输入： | 晶体 |
| 输出： | LVPECL |
| 电路数： | 1 |
| 比率 - 输入:输出： | 1:1 |
| 差分 - 输入:输出： | 无/是 |
| 频率 - 最大： | 900MHz |
| 除法器/乘法器： | 是/无 |
| 电源电压： | 3.135 V ~ 3.465 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-LQFP |
| 供应商设备封装： | 32-TQFP（7x7） |
| 包装： | 托盘 |
MPC9239
REVISION 2
DECEMBER 18, 2012
9
2012 Integrated Device Technology, Inc.
MPC9239 Data Sheet
900 MHz Low Voltage LVPECL Clock Synthesizer
Layout Recommendations
The MPC9239 provides sub-nanosecond output edge rates
and thus a good power supply bypassing scheme is a must.
Figure 6 shows a representative board layout for the MPC9239.
There exists many different potential board layouts and the one
pictured is but one. The important aspect of the layout in
GND for the bypass capacitors. Combining good quality general
purpose chip capacitors with good PCB layout techniques will
produce effective capacitor resonances at frequencies
adequate to supply the instantaneous switching current for the
MPC9239 outputs. It is imperative that low inductance chip
capacitors are used; it is equally important that the board layout
does not introduce back all of the inductance saved by using the
leadless capacitors. Thin interconnect traces between the
capacitor and the power plane should be avoided and multiple
large vias should be used to tie the capacitors to the buried
power planes. Fat interconnect and large vias will help to
minimize layout induced inductance and thus maximize the
series resonant point of the bypass capacitors. Note the dotted
lines circling the crystal oscillator connection to the device. The
oscillator is a series resonant circuit and the voltage amplitude
across the crystal is relatively small. It is imperative that no
actively switching signals cross under the crystal as crosstalk
energy coupled to these lines could significantly impact the jitter
of the device. Special attention should be paid to the layout of
the crystal to ensure a stable, jitter free interface between the
crystal and the on—board oscillator. Although the MPC9239
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 and bypass schemes discussed
in this section should be adequate to eliminate power supply
noise related problems in most designs.
Figure 6. PCB Board Layout Recommendation
for the PLCC28 Package
Using the On-Board Crystal Oscillator
The MPC9239 features a fully integrated on-board crystal
oscillator to minimize system implementation costs. The
oscillator is a series resonant, multivibrator type design as
opposed to the more common parallel resonant oscillator
design. The series resonant design provides better stability and
eliminates the need for large on chip capacitors. The oscillator
is totally self contained so that the only external component
required is the crystal. As the oscillator is somewhat sensitive to
loading on its inputs the user is advised to mount the crystal as
close to the MPC9239 as possible to avoid any board level
parasitics. To facilitate co-location surface mount crystals are
recommended, but not required. Because the series resonant
design is affected by capacitive loading on the XTAL terminals
loading variation introduced by crystals from different vendors
could be a potential issue. For crystals with a higher shunt
capacitance it may be required to place a resistance across the
terminals to suppress the third harmonic. Although typically not
required it is a good idea to layout the PCB with the provision of
adding this external resistor. The resistor value will typically be
between 500 and 1K
.
The oscillator circuit is a series resonant circuit and thus for
optimum performance a series resonant crystal should be used.
Unfortunately most crystals are characterized in a parallel
resonant mode. Fortunately there is no physical difference
between a series resonant and a parallel resonant crystal. The
difference is purely in the way the devices are characterized. As
a result a parallel resonant crystal can be used with the
MPC9239 with only a minor error in the desired frequency. A
parallel resonant mode crystal used in a series resonant circuit
will exhibit a frequency of oscillation a few hundred ppm lower
than specified, a few hundred ppm translates to kHz
inaccuracies. In a general computer application this level of
inaccuracy is immaterial. Table 12 below specifies the
performance requirements of the crystals to be used with the
MPC9239.
1
C2
CF
XTAL
C1
= VCC
= GND
= Via
Table 12. Recommended Crystal Specifications
Parameter
Value
Crystal Cut
Fundamental AT Cut
Resonance
Series Resonance1
1. See accompanying text for series versus parallel resonant
discussion.
Frequency Tolerance
75ppm at 25C
Frequency/Temperature Stability
150pm 0 to 70C
Operating Range
0 to 70
C
Shunt Capacitance
5-7pF
Equivalent Series Resistance (ESR)
50 to 80
Correlation Drive Level
100
W
Aging
5ppm/Yr (First 3 Years)
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相关代理商/技术参数 |
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| MPC9239ACR2 | 功能描述:时钟合成器/抖动清除器 RoHS:否 制造商:Skyworks Solutions, Inc. 输出端数量: 输出电平: 最大输出频率: 输入电平: 最大输入频率:6.1 GHz 电源电压-最大:3.3 V 电源电压-最小:2.7 V 封装 / 箱体:TSSOP-28 封装:Reel |
| MPC9239EI | 功能描述:时钟合成器/抖动清除器 FSL 900MHz LVPECL Freq. Synthesizer RoHS:否 制造商:Skyworks Solutions, Inc. 输出端数量: 输出电平: 最大输出频率: 输入电平: 最大输入频率:6.1 GHz 电源电压-最大:3.3 V 电源电压-最小:2.7 V 封装 / 箱体:TSSOP-28 封装:Reel |
| MPC9239EIR2 | 功能描述:时钟合成器/抖动清除器 RoHS:否 制造商:Skyworks Solutions, Inc. 输出端数量: 输出电平: 最大输出频率: 输入电平: 最大输入频率:6.1 GHz 电源电压-最大:3.3 V 电源电压-最小:2.7 V 封装 / 箱体:TSSOP-28 封装:Reel |
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