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参数资料
| 型号： | MK2049-44SILF |
| 元件分类： | 时钟产生/分配 |
| 英文描述： | 51.84 MHz, OTHER CLOCK GENERATOR, PDSO20 |
| 封装： | 0.300 INCH, SOIC-20 |
| 文件页数： | 4/9页 |
| 文件大小： | 176K |
| 代理商： | MK2049-44SILF |
3.3V Communications Clock PLL
MDS 2049-44 A
4
Revision 050203
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 295-9800 ●
www.icst.com
MK2049-44
Application Information
Output Frequency Configuration
The MK2049-44 is configured to generate a set of
output frequencies from an 8 kHz input clock. Please
refer to the Output Clock Selection Table on Page 2.
Input bits FS3:0 are set according to this table, as is the
external crystal frequency. Please refer to the Quartz
Crystal section on this page regarding external crystal
requirements.
Quartz Crystal
It is important that the correct type of quartz crystal is
used with the MK2049-44. Failure to do so may result in
reduced frequency pullability range, inability of the loop
to lock, or excessive output phase jitter.
The MK2049-44 operates by phase-locking the VCXO
circuit to the input signal of the selected ICLK input.
The VCXO consists of the external crystal and the
integrated VCXO oscillator circuit. To achieve the best
performance and reliability, a crystal device with the
recommended parameters (shown below) must be
used, and the layout guidelines discussed in the PCB
Layout Recommendations section must be followed.
The frequency of oscillation of a quartz crystal is
determined by its cut and by the external load
capacitance. The MK2049-44 incorporates variable
load capacitors on-chip which “pull”, or change, the
frequency of the crystal. The crystals specified for use
with the MK2049-44 are designed to have zero
frequency when the total of on-chip + stray capacitance
is 14 pF. To achieve this, the layout should use short
traces between the MK2049-44 and the crystal.
A complete description of the recommended crystal
parameters in the ICS application note, MAN05.
To obtain a list of qualified crystal devices please visit
our website at:
http://www.icst.com/products/telecom/vcxocrystals.htm
or email telecom@icst.com
PLL Loop Filter Components
All analog PLL circuits use a loop filter to establish
operating stability. The MK2049-44 uses external loop
filter components for the following reasons:
1) Larger loop filter capacitor values can be used,
allowing a lower loop bandwidth. This enables the use
of lower input clock reference frequencies and also
input clock jitter attenuation capabilities. Larger loop
filter capacitors also allow higher loop damping factors
when less passband peaking is desired.
2) The loop filter values can be user selected to
optimize loop response characteristics for a given
application.
Referencing the External Component Schematic on
this page, the external loop filter is made up of
components RS, CS and CP. RSET establishes PLL
charge pump current and therefore influences loop
filter characteristics.
A “normalized” PLL loop bandwidth may be calculated
as follows:
The “normalized” bandwidth equation above does not
take into account the effects of damping factor or the
second pole. However, it does provide a useful
approximation of filter performance.
The loop damping factor is calculated as follows:
Where:
RS = Value of resistor in loop filter (Ohms)
ICP = Charge pump current (amps)
(refer to Charge Pump Current Table, below)
N = Crystal multiplier shown in the above table
CS = Value of capacitor CS in loop filter (Farads)
CAP2
CAP1
5.6nF
750 k
0.56
F
Figure 3. Typical Loop Filter
R
Z
C2
C1
NBW
R
S
I
CP
×
575
×
N
----------------------------------------
=
Damping Factor
R
S
625
I
CP
×
C
S
×
N
------------------------------------------
×
=
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MK2049-45 | 制造商:ICS 制造商全称:ICS 功能描述:3.3V Communications Clock PLL |
| MK2049-45ASI | 功能描述:IC CLK PLL COMM 3.3V 20-SOIC RoHS:否 类别:集成电路 (IC) >> 时钟/计时 - 时钟发生器，PLL，频率合成器 系列:- 标准包装:39 系列:- 类型:* PLL:带旁路 输入:时钟 输出:时钟 电路数:1 比率 - 输入:输出:1:10 差分 - 输入:输出:是/是 频率 - 最大:170MHz 除法器/乘法器:无/无 电源电压:2.375 V ~ 3.465 V 工作温度:0°C ~ 70°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| MK2049-45ASILF | 功能描述:时钟发生器及支持产品 3.3 VOLT COMMUNICA. CLOCK VCXO PLL 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 |
| MK2049-45ASILFTR | 功能描述:时钟发生器及支持产品 3.3 VOLT COMMUNICA. CLOCK VCXO PLL 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 |
| MK2049-45ASITR | 功能描述:IC CLK PLL COMM 3.3V 20-SOIC RoHS:否 类别:集成电路 (IC) >> 时钟/计时 - 时钟发生器，PLL，频率合成器 系列:- 标准包装:39 系列:- 类型:* PLL:带旁路 输入:时钟 输出:时钟 电路数:1 比率 - 输入:输出:1:10 差分 - 输入:输出:是/是 频率 - 最大:170MHz 除法器/乘法器:无/无 电源电压:2.375 V ~ 3.465 V 工作温度:0°C ~ 70°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
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