参数资料
型号: ICS843253AGI-45LFT
厂商: IDT, Integrated Device Technology Inc
文件页数: 14/15页
文件大小: 0K
描述: IC SYNTHESIZER LVPECL 16-TSSOP
标准包装: 2,500
系列: HiPerClockS™, FemtoClock™
类型: 频率合成器
PLL: 带旁路
输入: 晶体
输出: LVCMOS,LVPECL,LVTTL
电路数: 1
比率 - 输入:输出: 1:3
差分 - 输入:输出: 无/是
频率 - 最大: 156.25MHz
除法器/乘法器: 是/无
电源电压: 3.135 V ~ 3.465 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 16-TSSOP(0.173",4.40mm 宽)
供应商设备封装: 16-TSSOP
包装: 带卷 (TR)
其它名称: 843253AGI-45LFT
ICS843253I-45
FEMTOCLOCK CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER
ICS843253AGI-45 REVISION A JULY 20, 2009
8
2009 Integrated Device Technology, Inc.
LVCMOS to XTAL Interface
The XTAL_IN input can accept a single-ended LVCMOS signal
through an AC coupling capacitor. A general interface diagram is
shown in Figure 3. The XTAL_OUT pin can be left floating. The input
edge rate can be as slow as 10ns. For LVCMOS signals, it is
recommended that the amplitude be reduced from full swing to half
swing in order to prevent signal interference with the power rail and
to reduce noise. This configuration requires that the output
impedance of the driver (Ro) plus the series resistance (Rs) equals
the transmission line impedance. In addition, matched termination at
the crystal input will attenuate the signal in half. This can be done in
one of two ways. First, R1 and R2 in parallel should equal the
transmission line impedance. For most 50
applications, R1 and R2
can be 100
. This can also be accomplished by removing R1 and
making R2 50
.
Figure 3. General Diagram for LVCMOS Driver to XTAL Input Interface
Termination for 3.3V LVPECL Outputs
The clock layout topology shown below is a typical termination for
LVPECL outputs. The two different layouts mentioned are
recommended only as guidelines.
The differential outputs are low impedance follower outputs that
generate ECL/LVPECL compatible outputs. Therefore, terminating
resistors (DC current path to ground) or current sources must be
used for functionality. These outputs are designed to drive 50
transmission lines. Matched impedance techniques should be used
to maximize operating frequency and minimize signal distortion.
Figures 4A and 4B show two different layouts which are
recommended only as guidelines. Other suitable clock layouts may
exist and it would be recommended that the board designers
simulate to guarantee compatibility across all printed circuit and clock
component process variations.
Figure 4A. 3.3V LVPECL Output Termination
Figure 4B. 3.3V LVPECL Output Termination
XTAL_IN
XTAL_OUT
Ro
Rs
Zo = Ro + Rs
50
0.1f
R1
R2
VCC
3.3V
V
CC - 2V
R1
50
R2
50
RTT
Z
o = 50
Z
o = 50
+
_
RTT =
* Z
o
1
((V
OH + VOL) / (VCC – 2)) – 2
3.3V
LVPECL
Input
R1
84
R2
84
3.3V
R3
125
R4
125
Z
o = 50
Z
o = 50
LVPECL
Input
3.3V
+
_
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