模数转换器（ADC）的基本原理ADI

简介：ADI新型转换器

问：我们都知道采样率和分辨率都会影响到AD/DA转换器的精度。请问Analog Deviced公司的工程师，你们公司是怎么样提高自己产品的精度，你们最好的产品精度能够做到什么程度？
答： We have many expert that have more than 10 years design experience. The best ADC:AD7738 24 bit 0.05 ~ 12.3K , AD7674:18 bit SAR @800k, AD7677: 16bit SAR @1MHz, AD6645: 14bit @ 105MHz, AD9430: 12bit @ 210MHz.

问：我现在正在做一个采集纳伏数量级的数据采集卡,是基于计算机ISA总线的.采集这样的微弱信号,要用到低噪声,高精度放大器,然后再接至AD,如何解决阻抗匹配的问题?设计电路的时候有哪些原则?
答： Use JFET such as AD8610 input OP if for high impendence source. The ADC should driver by a hign signal level AMP.
Please pay attentation to lay out , shielding and power supply. Use a DC-DC then use Lineary regulate such as ADP3335 LDO.

问：What"s the different of the AD775X and CS54XX?Can I use AD775x instead of CS54XX?
答： This question relates to our application specific products targeted at energy metering applications. Can you please contact harry.wu@analog.com regarding questions on these products.

问：3.3V工作电压的16位AD converter，理论上应能够分辨出3.3*1000000/65535=50.35μV的电压变化，但通常数字模拟混合电路板的噪声电压要远远大于这一数值,例如电压基准源LM336-2.5的标称电压变化典型值为2.6mV，请问高精度的ADC在电路板布线和选择ADC的模拟参考电源方面的要求是什么？提高ADC采样精度的措施有哪些？谢谢。
答： Therefore the reference accuracy is very important, so you just need to select best reference. For precision ADC, you need to note PCB layout, supply de-coupling, grounding. Also you can use oversampling, nose shaping (sigma delta) ADC, and other technolog

问：在PIPELINED ADC中,采样速率是30M,那么运放在30M时的放大倍数应该达到多少呢?
答： I think this should be the bnadwidth issue than the gain. The OP-Amp -3db BW should better than 15MHz.

问：AD6640对时钟输入有什么要求？为什么要通过变压器输入？
答： Low clock jetter is need for hagh speed ADC such as AD6640 (12bit, 65M ) and AD6644 (14bit, 65M).
The signal-to-noise ratio (SNR) for an ADC can be predicted.
When normalized to ADC codes, Equation 1 accurately predicts
the SNR based on three

问：问：ADI公司的高速ADC中12位的最快的可以达到210MSPS，请问怎样设计这样的数据接口和存储，以及评估处理的速度，如果做频谱分析用FPGA好，还是DSP好，若用DSP并行怎样确定共享的连接？另假设要采集更高的信号（例如150MHz的带宽），是否可以用并行工作的方法实现而只用内部的采样保持电路（用分相时钟？）？
答： AD9430 can up to 210MSPS. On this architecture, we provide dul channels output. Your design have to provide this dual data interface for it. For the spectrum analyzer that I would like to suggest you to use DSP such as ADSP-21161 on this that he not just o

问：1. A/D前,应采用何种低通滤波器(有源还是无源).
2. 模拟输入电压大小受那些限制
答： 1) It depends on you application, and system request. Basically you should note that active filter can bring gain, but noise as well, passive filter is without gain, so has some power loss, but with better noise preformance. You can refer to below link for

问：请问采样率和转换速度有和联系？
答： This relates to the architecture of the ADC. If it is SAR, pipeline or flash ADC, if sampling rate is high then the conversion speed is high. If it is sigma-delta ADC, then this will be decided by the internal structure of the ADC.

问：现在的高速ADC在设计上，怎样考虑电源、地平面的铺设减少噪声确保转换精度和可靠性？能否提供一些具体的测试实例或分析仿真结果，不要只是定性的描述。谢谢。
答： OK, in fact we have the materials that explain in detail to this question with examples.

Please refer to the link below:
http://www.analog.com/technology/amplifiersLinear/training/highspeed.html