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參數(shù)資料
| 型號： | MPC92439FN |
| 廠商： | INTEGRATED DEVICE TECHNOLOGY INC |
| 元件分類： | 時(shí)鐘產(chǎn)生/分配 |
| 英文描述： | 900 MHz, OTHER CLOCK GENERATOR, PQCC28 |
| 封裝： | PLASTIC, LCC-28 |
| 文件頁數(shù)： | 13/13頁 |
| 文件大?。?/td> | 840K |
| 代理商： | MPC92439FN |
MPC92439
900MHZ, LOW VOLTAGE, LVPECL CLOCK SYNTHESIZER
IDT / ICS LVPECL CLOCK SYNTHESIZER
9
MPC92439 REV 3 JANUARY 7, 2008
of isolation may be required. The simplest form of isolation is a
power supply filter on the VCC_PLL pin for the MPC92439.
Figure 7 illustrates a typical power supply filter scheme. The
MPC92439 is most susceptible to noise with spectral content in
the 1 kHz to 1 MHz range. Therefore, the filter should be
designed to target this range. The key parameter that needs to
be met in the final filter design is the DC voltage drop that will
be seen between the VCC supply and the MPC92439 pin of the
MPC92439. From the data sheet, the VCC_PLL current (the
current sourced through the VCC_PLL pin) is maximum 20 mA,
assuming that a minimum of 2.835 V must be maintained on the
resistance of 10–15
to meet the voltage drop criteria. The RC
filter pictured will provide a broadband filter with approximately
100:1 attenuation for noise whose spectral content is above
20 kHz. 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. Generally, the resistor/capacitor filter will
be cheaper, easier to implement and provide an adequate level
of supply filtering. A higher level of attenuation can be achieved
by replacing the resistor with an appropriate valued inductor. A
1000
H choke will show a significant impedance at 10 kHz
frequencies and above. Because of the current draw and the
voltage that must be maintained on the VCC_PLL pin, a low DC
resistance inductor is required (less than 15
).
Figure 7. VCC_PLL Power Supply Filter
Layout Recommendations
The MPC92439 provides sub-nanosecond output edge rates
and thus a good power supply bypassing scheme is a must.
Figure 8 shows a representative board layout for the
MPC92439. There exists many different potential board layouts
and the one pictured is but one. The important aspect of the
layout in Figure 8 is the low impedance connections between
VCC and 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 MPC92439 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 MPC92439 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 8. PCB Board Layout Recommendation
for the PLCC28 Package
The On-Chip Crystal Oscillator
The MPC92439 features an integrated on-chip crystal
oscillator to minimize system implementation cost. The
integrated oscillator is a Pierce-type that uses the crystal in its
parallel resonance mode. It is recommended to use a
10 to 20 MHz crystal with a load specification of CL =10 pF.
Crystals with a load specification of CL = 20 pF may be used at
the expense of an slightly higher frequency than specified for
the crystal. Externally connected capacitors on both the
XTAL_IN and XTAL_OUT pins are not required but can be used
to fine-tune the crystal frequency as desired.
The crystal, the trace and optional capacitors should be
placed on the board as close as possible to the MPC92439
XTAL_IN and XTAL_OUT pins to reduce crosstalk of active
VCC_PLL
VCC
MPC92439
C1, C2 = 0.01...0.1 F
VCC
CF = 22 F
RF = 10-15
C2
C1
1
C2
CF
XTAL
C1
= VCC
= GND
= Via
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MPC92439KLF | 制造商:IDT 制造商全稱:Integrated Device Technology 功能描述:900MHz, Low Voltage, LVPECL Clock Syntheesizer |
| MPC92469 | 制造商:IDT 制造商全稱:Integrated Device Technology 功能描述:400 MHz Low Voltage PECL Clock Synthesizer w/Spread Spectrum |
| MPC92469AC | 功能描述:時(shí)鐘合成器/抖動清除器 LVPECL Clock Synthesizer RoHS:否 制造商:Skyworks Solutions, Inc. 輸出端數(shù)量: 輸出電平: 最大輸出頻率: 輸入電平: 最大輸入頻率:6.1 GHz 電源電壓-最大:3.3 V 電源電壓-最小:2.7 V 封裝 / 箱體:TSSOP-28 封裝:Reel |
| MPC92469ACR2 | 功能描述:IC SYNTHESIZER LVPECL 32-LQFP RoHS:是 類別:集成電路 (IC) >> 時(shí)鐘/計(jì)時(shí) - 時(shí)鐘發(fā)生器，PLL，頻率合成器 系列:- 標(biāo)準(zhǔn)包裝:1,000 系列:- 類型:時(shí)鐘/頻率合成器，扇出分配 PLL:- 輸入:- 輸出:- 電路數(shù):- 比率 - 輸入:輸出:- 差分 - 輸入:輸出:- 頻率 - 最大:- 除法器/乘法器:- 電源電壓:- 工作溫度:- 安裝類型:表面貼裝 封裝/外殼:56-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:56-VFQFP-EP（8x8） 包裝:帶卷 (TR) 其它名稱:844S012AKI-01LFT |
| MPC9259 | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:900 MHz LOW VOLTAGE LVDS CLOCK SYNTHESIZER |
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