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参数资料
| 型号： | ADCLK846/PCBZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 5/16页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION FOR ADCLK846 |
| 设计资源： | Synchronizing Multiple AD9910 1 GSPS Direct Digital Synthesizers (CN0121) |
| 标准包装： | 1 |
| 主要目的： | 计时，时钟缓冲器 / 驱动器 / 接收器 / 变换器 |
| 已用 IC / 零件： | ADCLK846 |
| 主要属性： | 6 LVDS/12 CMOS 输出 |
| 次要属性： | CMOS，LVDS 输出 |
| 已供物品： | 板 |
ADCLK846
Rev. B | Page 13 of 16
APPLICATIONS INFORMATION
USING THE ADCLK846 OUTPUTS FOR ADC CLOCK
APPLICATIONS
Any high speed analog-to-digital converter (ADC) is extremely
sensitive to the quality of the sampling clock provided by the
user. An ADC can be thought of as a sampling mixer, and any
noise, distortion, or timing jitter on the clock is combined with
the desired signal at the ADC output. Clock integrity require-
ments scale with the analog input frequency and resolution,
with higher analog input frequency applications at ≥14-bit
resolution being the most stringent. The theoretical SNR of
an ADC is limited by the ADC resolution and the jitter on
the sampling clock. Considering an ideal ADC of infinite
resolution where the step size and quantization error can be
ignored, the available SNR can be expressed approximately by
=
J
AT
f
SNR
2π
1
20log
where:
fA is the highest analog frequency being digitized.
TJ is the rms jitter on the sampling clock.
Figure 24 shows the required sampling clock jitter as a function
of the analog frequency and effective number of bits (ENOB).
See AN-756 Application Note and AN-501 Application Note
for more information.
fA FULL-SCALE SINE WAVE ANALOG FREQUENCY (MHz)
S
NR
(
d
B
)
EN
O
B
10
1k
100
30
40
50
60
70
80
90
100
110
6
8
10
12
14
16
18
T
J
= 100f
S
200f
S
400f
S
1ps
2ps
10ps
SNR = 20log
1
2πfATJ
07
22
6-
02
7
Figure 24. SNR and ENOB vs. Analog Input Frequency
Many high performance ADCs feature differential clock inputs
to simplify the task of providing the required low jitter clock on
a noisy PCB. Distributing a single-ended clock on a noisy PCB
can result in coupled noise on the sample clock. Differential
distribution has inherent common-mode rejection that can
provide superior clock performance in a noisy environment.
The ADCLK846 features LVDS outputs that provide differential
clock outputs, which enable clock solutions that maximize con-
verter SNR performance. Consider the input requirements of
the ADC (differential or single-ended, logic level, termination)
when selecting the best clocking/converter solution.
LVDS CLOCK DISTRIBUTION
The ADCLK846 provides clock outputs that are selectable
as either CMOS or LVDS level outputs. LVDS is a differential
output option that uses a current-mode output stage. The
nominal current is 3.5 mA, which yields 350 mV output swing
across a 100 Ω resistor. The LVDS output meets or exceeds all
ANSI/TIA/EIA-644 specifications. A recommended termina-
tion circuit for the LVDS outputs is shown in Figure 25.
If ac coupling is necessary, place decoupling capacitors either
before or after the 100 Ω termination resistor.
VS
LVDS
100
DIFFERENTIAL (COUPLED)
VS
LVDS
100
0
722
6-
0
28
Figure 25. LVDS Output Termination
See the AN-586 Application Note at www.analog.com for more
information on LVDS.
CMOS CLOCK DISTRIBUTION
The output drivers of the ADCLK846 can also be configured
as CMOS drivers. When selected as a CMOS driver, each
output becomes a pair of CMOS outputs. These outputs are
1.8 V CMOS compatible.
When single-ended CMOS clocking is used, some of the
following guidelines outlined in this section apply.
Design point-to-point connections such that each driver has
only one receiver, if possible. Connecting outputs in this manner
allows for simple termination schemes and minimizes ringing
due to possible mismatched impedances on the output trace.
Series termination at the source is generally required to provide
transmission line matching and/or to reduce current transients
at the driver.
The value of the resistor is dependent on the board design and
timing requirements (typically 10 Ω to 100 Ω is used). CMOS
outputs are also limited in terms of the capacitive load or trace
length that they can drive. Typically, trace lengths less than
3 inches are recommended to preserve signal rise/fall times
and signal integrity.
CMOS
10
60.4
(1.0 INCH)
MICROSTRIP
07
22
6-
07
6
Figure 26. Series Termination of CMOS Output
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ADCLK854 | 制造商:AD 制造商全称:Analog Devices 功能描述:1.8 V, 12-LVDS/24-CMOS Output, Low Power Clock Fanout Buffer |
| ADCLK854/PCBZ | 功能描述:BOARD EVALUATION FOR ADCLK845 RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:- 标准包装:1 系列:PSoC® 主要目的:电源管理，热管理 嵌入式:- 已用 IC / 零件:- 主要属性:- 次要属性:- 已供物品:板，CD，电源 |
| ADCLK854BCPZ | 功能描述:IC CLOCK BUFFER MUX 2:12 48LFCSP RoHS:是 类别:集成电路 (IC) >> 时钟/计时 - 时钟缓冲器，驱动器 系列:- 产品培训模块:High Bandwidth Product Overview 标准包装:1,000 系列:Precision Edge® 类型:扇出缓冲器（分配） 电路数:1 比率 - 输入:输出:1:4 差分 - 输入:输出:是/是 输入:CML，LVDS，LVPECL 输出:CML 频率 - 最大:2.5GHz 电源电压:2.375 V ~ 2.625 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:16-VFQFN 裸露焊盘，16-MLF? 供应商设备封装:16-MLF?（3x3） 包装:带卷 (TR) |
| ADCLK854BCPZ-REEL7 | 功能描述:IC CLOCK BUFFER MUX 2:12 48LFCSP RoHS:是 类别:集成电路 (IC) >> 时钟/计时 - 时钟缓冲器，驱动器 系列:- 标准包装:74 系列:- 类型:扇出缓冲器（分配） 电路数:1 比率 - 输入:输出:1:10 差分 - 输入:输出:是/是 输入:HCSL, LVCMOS, LVDS, LVPECL, LVTTL 输出:HCSL，LVDS 频率 - 最大:400MHz 电源电压:3 V ~ 3.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:32-VFQFN 裸露焊盘 供应商设备封装:32-QFN（5x5） 包装:管件 |
| ADCLK905 | 制造商:AD 制造商全称:Analog Devices 功能描述:Ultrafast SiGe ECL Clock/Data Buffers |
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