- 您现在的位置：买卖IC网 > PDF目录166397 > B900J24PXX12I 0-BIT, 80 MHz, OTHER DSP, PQFP44 PDF资料下载
参数资料
| 型号： | B900J24PXX12I |
| 元件分类： | 数字信号处理 |
| 英文描述： | 0-BIT, 80 MHz, OTHER DSP, PQFP44 |
| 文件页数： | 95/100页 |
| 文件大小： | 1547K |
| 代理商： | B900J24PXX12I |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页第35页第36页第37页第38页第39页第40页第41页第42页第43页第44页第45页第46页第47页第48页第49页第50页第51页第52页第53页第54页第55页第56页第57页第58页第59页第60页第61页第62页第63页第64页第65页第66页第67页第68页第69页第70页第71页第72页第73页第74页第75页第76页第77页第78页第79页第80页第81页第82页第83页第84页第85页第86页第87页第88页第89页第90页第91页第92页第93页第94页当前第95页第96页第97页第98页第99页第100页
B900
Advance Data Sheet
Baseband Signal Processor
July 1999
94
Lucent Technologies Inc.
9 Crystal Oscillator Electrical Requirements and Characteristics (continued)
9.2
Frequency Accuracy Considerations
For most applications, clock frequency errors in the hundreds of parts per million (ppm) can be tolerated with no
adverse effect. However, for applications where precise frequency tolerance on the order 100 ppm is required, care
must be taken in the choice of external components (crystal and capacitors) as well as in the layout of the printed-
circuit board. Several factors determine the frequency accuracy of a crystal-based oscillator circuit. Some of these
factors are determined by the properties of the crystal itself. Generally, a low-cost, standard crystal is not sufficient
for a high-accuracy application, and a custom crystal must be specified. Most crystal manufacturers provide exten-
sive information concerning the accuracy of their crystals, and an applications engineer from the crystal vendor
should be consulted prior to specifying a crystal for a given application.
In addition to absolute, temperature, and aging tolerances of a crystal, the operating frequency of a crystal is also
determined by the total load capacitance seen by the crystal. When ordering a crystal from a vendor, it is neces-
sary to specify a load capacitance at which crystal operating frequency is measured. Variations in this load capaci-
tance due to temperature and manufacturing variations cause variations in the operating frequency of the oscillator.
Figure 27 illustrates some of the sources of this variation.
CEXT = External load capacitor (one each required for XTALA and XTALB)
CD = Parasitic capacitance of the B900 itself
CB = Parasitic capacitance of the printed-wiring board
CO = Parasitic capacitance of crystal (not part of CL, but still a source of frequency variation)
CL = Calculated load capacitance to be provided to crystal vendor
5-4045.r3
Figure 27. Components of Load Capacitance for Crystal Oscillator
The load capacitance, CL, must be specified to the crystal vendor. The crystal manufacturer cuts the crystal so that
the frequency of oscillation is correct when the crystal sees this load capacitance. Note that C L refers to a capaci-
tance seen across the crystal leads, meaning that for the circuit shown in Figure 27, CL is the series combination of
the two external capacitors (CEXT/2) plus the equivalent board and device strays (CB/2 + CD/2). For example, if
10 pF external capacitors were used and parasitic capacitance is neglected, the crystal should be specified for a
load capacitance of 5 pF. If the load capacitance deviates from this value due to the tolerance on the external
capacitors or the presence of parasitic capacitance, the frequency also deviates. This change in frequency as a
function of load capacitance is known as pullability, which is expressed in units of ppm/pF.
CD
XTAL
XTAL1/2A
XTAL1/2B
CL
CB
CEXT
CD
CB
CEXT
CO
相关PDF资料 |
PDF描述 |
|---|---|
| B900J24FXX12IT | 0-BIT, 59.88 MHz, OTHER DSP, PQFP44 |
| BA00CC0WCP-V5 | 1A Low Dropout Voltage Regulator with Shut Down Switch(Adustable Voltage) |
| BA10E6 | COPPER ALLOY, TIN FINISH, RING TERMINAL |
| BA12004 | 0.5 A, 7 CHANNEL, NPN, Si, POWER TRANSISTOR |
| BA1518SUR5VP | SINGLE COLOR DISPLAY CLUSTER, ULTRA RED |
相关代理商/技术参数 |
参数描述 |
|---|---|
| B-900-M-10 | 制造商:Thomas & Betts 功能描述: |
| B-900-M-10-EG | 制造商:Thomas & Betts 功能描述: |
| B-900-M-20 | 制造商:Thomas & Betts 功能描述: |
| B-900-M-20-EG | 制造商:Thomas & Betts 功能描述: |
| B901 | 制造商:EDAL 制造商全称:EDAL 功能描述:Silicon Bridge Rectifier |
发布紧急采购，3分钟左右您将得到回复。