類比數位轉換器的基本原理（臺灣）-National Semiconductor厂商_在线座谈

精彩问答

主题：模拟数字转换器的基本原理
在线问答：
[问：gihrong]	请教一下SAR ADC 大约应用在那边？谢谢
[答：Daniel]	You can use SAR ADC at many application. Most of the cases, people likes to use SAR ADC with serial interface so that we have smaller PCB size.	[2005-3-10 14:28:10]
[问：ts_li04]	模拟数字转换器的优势在那里?
[答：Daniel]	Comparing to comparator, we can use ADC to get more resolution from input signals. In some cases, ADC is used as the bridge between anlaog world (sensors) and digital world (CPU, MCU or DSP).	[2005-3-10 14:31:19]
[问：德森蜜]	为了有系统的精进专业不知贵单位可有机会在台湾新竹地区开办中短期专业理论实作的课程呢? 谢谢!
[答：Daniel]	We can think about this suggestion, but for the schedule we need to discuss with our colleagues to give you answer. If possible, I recommend you can contact with our sales office for more information. Once we have courses, we can inform you by phone or by email.	[2005-3-10 14:32:37]
[问：minchieh]	模拟信号转换为数字信号的过程中,对于模拟信号loss或bit error,所采取的补偿方式如何?
[答：Stanley]	first,you can check SNR,THD and resolution DC and AD performance, you can add compensate circuit to match it. thanks!	[2005-3-10 14:33:50]
[问：foxr47]	如何确保A/D的精确度没有问题 and 如何测试 A/D 精确度有符合规格
[答：Daniel]	You need a very accurate signal generator and measure ADC with logic analyzers together a good power supply.	[2005-3-10 14:34:00]
[问：IBM007]	dear compere, would you please demostrate ADC/DAC application in medical field
[答：Daniel]	National will provide Signal Path Seminar very soon, and medical is one of topics we"ll demo at that time.	[2005-3-10 14:34:56]
[问：jason_ko]	请问要如何选用适当之ADC?
[答：Stanley]	according to your sysytem requirement, choose right ADC for your application,two points for your refernce: DC performance: resolution, sampling rate,gain earra ... AC performance: SNR, THD and SFDR... Thanks!	[2005-3-10 14:36:23]
[问：robinm]	可否简单介绍delta-sigma的工作原理和应用
[答：Daniel]	We usually explain it with Digital concept. You can image that we sample at a signal 1000 times, and then compute the average value and delta value (variation). While we have the normal distribution of the data, then we can know which value could the most possible value in the real world. Inside Sigmat-Delta ADC, we do it in Analog way (use capacitors).	[2005-3-10 14:37:04]
[问：simoncts]	请使用何种简易仪表快速量测并且除错
[答：Stanley]	what do you want to solve, more detail? thanks!	[2005-3-10 14:37:30]
[问：jackie_wang]	请问应用于手机上如何用ADC来做声音大小的显示贵公司有何Solution?
[答：Daniel]	We made a demo to use ADC as an 1-wire remote key detection, we show the simple schematics on the presentation file.	[2005-3-10 14:38:20]
[问：fanl]	请谈一下，影响ADC频率进一步提高的主要障碍在什么地方？谢谢
[答：Daniel]	Mainly at ADC"s architecture ,like Sigma-Delta ADC to SAR ADC (20MSPS), from flash to pipeline (200MSPS). If you want faster, you still need to check if your process can support it or not.	[2005-3-10 14:39:55]
[问：fingure]	比如三x的老手机，就是掉完第一格电，后来的两格电掉的比较快，请问用ADC怎样实现转换？（Detail）
[答：Stanley]	we can get the voltage from Battery, then convert it to digit signal to mcu, then display it on screen. thanks!	[2005-3-10 14:40:25]
[问：fish272]	谢谢请问对于改变比特数可否解释的更详细一点？用软件如何编程，流程怎样？要接单片机吗？还想改变采样频率不知与时钟有关吗？ADC用内部含时钟的还是外部加个晶振？是否也要编程？
[答：Daniel]	If you use an 8bits SAR ADC, then you will receive 8bits from it. If you likes to have less than 8 bits data, then you can drop it by your MCU.	[2005-3-10 14:41:01]
[问：hbli]	您刚才讲了flash ADC，请问电子平均技术是怎么回事？
[答：Stanley]	since there are Large Number of Comparators (2n - 1)in flash ADC, they must be closely matched	[2005-3-10 14:41:51]
[问：wangquancai8]	模数转换的信噪比做得怎样?转换速率最高多少MSPS?
[答：Stanley]	very good, up to dual 1.5GSPS. thanks!	[2005-3-10 14:44:11]
[问：bluenotes]	Is the continuous time sigma-delta technique useful and practical in the future? Thanks for your answering.
[答：Daniel]	Well, it depends on your application. Sigma-Delta ADC is very accurate but the sample rate is very low. That is, you can use it only when you want to sample some very low speed signal. It"s quite useful at power detection or power monitor system.	[2005-3-10 14:44:35]
[问：fish272]	is sample frequency and sample rate the same?
[答：Stanley]	they are same.	[2005-3-10 14:44:42]
[问：wei1201]	ADC和DAC都有SNR的spec，请问影响其SNR的主要关键因素为何？又使用者如何能量测到ADC和DAC的SNR?
[答：Daniel]	You need to use accurate signal generator and power supply to send voltage to ADC, and then use logic analyzer to collect output data so that you can compute ADC"s SNR.	[2005-3-10 14:46:42]
[问：hbli]	SAR ADC中的DAC设计时，采用什么样的结构？如果产生失配如何解决？
[答：Daniel]	It"s up to your design methodology or the limitation of the process you used.	[2005-3-10 14:47:56]
[问：bluenotes]	What"s the most powerful application of CT sigma-delta ADC in next few years?
[答：Stanley]	For CT application, some ADC in MCU, some outside. it is the trend which is outside ADC, more high speed and high precision will be powerful. thanks.	[2005-3-10 14:48:46]
[问：GYQ]	能否提供应用的例子？致谢！
[答：Daniel]	Could you specify what kind of examples you want to hear from us?? We plan to have another seminar to discuss about ADC application later.	[2005-3-10 14:48:55]
[问：ncyang]	what"s the key for high speed , high resolution ADC
[答：Daniel]	Key spec or key issue to design with high speed ADC?? I think the first one should be "how to choose the right ADC??", and then the design/layout skills to handle ADC on your PCB.	[2005-3-10 14:50:02]
[问：fanl]	对于AD/DA在WLAN（802.11g）上的应用，贵公司对应的解决方案是什么？
[答：Daniel]	If you"re talking about clint side, it has already been integrated into WLAN chipset. But if you want some solution for AP side, then I recommend you to ADC08100/ADC08060 for lower cost, or ADC12040/ADC12066 for high performance.	[2005-3-10 14:52:01]
[问：whuhq2000]	我比较感兴趣ADC在测量系统的应用
[答：Daniel]	How fast do you want to measure your target?? We have ADC08D1000 which is 8bits and 1000MHz sample rate part. It"s the best part we can see in the whole world for digital scope design.	[2005-3-10 14:53:11]
[问：fengzejin]	现在的转换器朝哪个方向发展
[答：Daniel]	High speed and high resolution.	[2005-3-10 14:53:38]
[问：Nickwu703]	1.高速ADC与低速ADC之区分与应用？
[答：Daniel]	The architecture of high speed ADC and low speed ADC is different. Low speed ADC can be anywhere and used in any system. For examples, there are some ADC which have been used in portable devices to detect voltage or current.	[2005-3-10 14:56:23]
[问：wy_niu]	What"s input voltage sewing？
[答：Stanley]	it is voltage edge slew fast or slow	[2005-3-10 14:56:33]
[问：bjbdlzb]	ADC的数字地与模拟地的电压差最大可以达到多少？
[答：Daniel]	General case is 1V (for higher speed ADC) to close VCC (lower speed ADC), but it can not be over VCC.	[2005-3-10 14:57:22]
[问：bellsleep]	在ADC的模拟输入方面有没有需要注意的?比如阻抗匹配方面?
[答：Stanley]	Yes,you are right,others here is list for you : Inadequate Supply Bypassing Inadequate VA - VDR* Supply Decoupling Noisy Components/Conditioning Circuitry Quantization Clock Output to Input Coupling	[2005-3-10 14:58:23]
[问：fish272]	对于时钟，采样频率和比特数仍有疑问：您是说如果有8个时钟沿就会输出8比特？这个时钟指的是什莫？如果选用晶振如何解释？
[答：Daniel]	It"s internal clock which has been used inside ADC, but we need to provide it from external components. It can be from MCU I/O pin or external oscillator (not from crystal).	[2005-3-10 14:59:13]
[问：hbli]	SAR ADC结构中的比较器采用静态比较器还是动态比较器？应该注意那些问题？
[答：Daniel]	We usually use dynamic one to get faster speed. You don"t need to care about it because we had already integrated it into ADC. The only thing you need to pay attention is to provide clean power to ADC.	[2005-3-10 15:00:34]
[问：achunghuang]	下次座谈能否谈一下sigma delta adc 呢?thans
[答：Stanley]	Yes, we will, when we have Sigma delta ADC,we will let you know, for more information, you can log on: http://www.national.com/appinfo/adc/ thanks for your advise.	[2005-3-10 15:01:23]
[问：hzzhangxin]	分辨率和速率是ADC的一对矛盾，有没有使他们同时都达到高性能的方法？
[答：Daniel]	yes, money can make it happen. :-) That is, you have to pay a lot of money to have a highest speed and highest bit resolution ADC. From my perception, I recommend you to choose a sufficient one in your application.	[2005-3-10 15:02:18]
[问：hbli]	刚才您讲的SAR ADC的前端实际设计时用不用加S/H电路
[答：Stanley]	We have S/H circuit in ADC, thanks!	[2005-3-10 15:02:48]
[问：ts_li04]	模拟数字转换器的应用领域?
[答：Daniel]	If you want to control or detect the real world with your MCU, CPU or DSP, then you need to use ADC.	[2005-3-10 15:03:20]
[问：wei1201]	which kind of ADC best suits speech processing applications?
[答：Daniel]	If you want it very accurate, then I recommend you to use Sigma-Delta ADC.	[2005-3-10 15:04:36]
[问：fish272]	对于采样频率，时钟和比特数仍有疑问：你实说有8个时钟沿就输出8比特和转换器的寄存器没有关系？这个时钟指的是什莫？可否用内部含时钟的转换器，如果外加晶振呢？如果用单片机内置的A/D 应该怎样改变比特数，与时钟有关吗？是否更复杂？
[答：Stanley]	here is our website address explaining for you: pls see: http://www.national.com/AU/design/1,4678,8_0_,00.html thanks!	[2005-3-10 15:05:30]
[问：yhyang]	所以主要影响SNR的因素是来自于quantization error吗？
[答：Daniel]	Not exactly, most of them are from the parameters of your ADC architectures, like comparators or DAC in SAR ADC.	[2005-3-10 15:05:36]
[问：ecnanjing _EBY7E]	噪音与AD/DA的位数有何关系？
[答：Daniel]	Frankly speaking, no solid and direct relation. But people often use higher bit resolution to prevent some trucation error.	[2005-3-10 15:07:25]
[问：fingure]	ADC and DAC used in oscillograph,speed is the important issue,which models are for oscillograph?
[答：Daniel]	We have the best part for it, ADC08D1000, 8 bits and 1000MHZ sample rate. We"ll have 1500MHz sample rate part very soon.	[2005-3-10 15:08:55]
[问：wei1201]	请问ADC、DAC之SNR好坏的影响关键因素为何？使用者如何能验证ADC、DAC的SNR？
[答：Stanley]	it will impact ENOB which is related with SNR and THD.NS have waveVision demo board test for you to verify. thanks!	[2005-3-10 15:09:21]
[问：ecnanjing _EBY7E]	请问NS专家，贵公司是否有直接输出1-40mA的电流型DAC？
[答：Daniel]	yes, you can check on our website, www.national.com for the detailed information.	[2005-3-10 15:09:44]
[问：hzzhangxin]	现在最高的是24BITADC，能否有突破？
[答：Daniel]	From theory viewpoint, we can have higher resolution. But from the real application, you can get a lot of random noise from ADC if we don"t resolve the power/ground noise issue.	[2005-3-10 15:14:35]
[问：hbli]	实际设计ADC中，常加滤波电容、旁路电容等，加在那里？加多大？
[答：Daniel]	You must have bypass capacitor for power/ground, and also reference voltage. For the filter capacitor, we usually put it at the signal chain, i.e., the input siangl pin to ADC.	[2005-3-10 15:16:24]
[问：tudan]	对于应用在audio的delta sigma ADC 在量测其SNR时我们为避免所谓overload的现象通常部会输入full 的Vin 而改以较小的Vin 来量测请问贵公司通常会以多少为量测标准?( such as -60dB )
[答：Stanley]	increase Vin to have good SNR. what is -60db for, more details.pls advise thanks!	[2005-3-10 15:17:31]
[问：robinm]	Does it mean that you NS don"t have sigma delta ADC right now?
[答：Daniel]	We integrate this kind of ADC into different parts, like Audio, temp sensor, current sensor... and so on. But we haven"t released over 20 bits Sigma-Delta ADC now.	[2005-3-10 15:17:37]
[问：hbli]	请问数字IF接收机中如果用ADC，那么它的性能指标大概是多少？一般采样什么结构？
[答：Stanley]	it is about 12 bit ADC and about 60Msps, basically, it is pipeline arch.	[2005-3-10 15:18:45]
[问：ecnanjing _EBY7E]	我做土壤酸碱度分析，输入信号为nA级电平信号，放大后AD，在由MCU处理显示，请问NS有什么器件可推荐，主要是弱信号放大和ADC。
[答：Daniel]	You may need several order amplifier for your system, so I recommend you to use our LMH2011/2012/2013 precision amplifer.	[2005-3-10 15:19:05]
[问：starluck]	请问conversion time和sample frequency是什么关系？
[答：Daniel]	In SAR ADC, we can not say we sample the signal at one or two clock because we need more than 12 clocks to convert the input signal to digital data. But we can sample and convert the signal almost within one or two clocks if we use high speed ADC. So, we often mention conversion time for SAR ADC and Sigma-Delta ADC.	[2005-3-10 15:22:41]
[问：hbli]	在设计ADC时，系统级仿真主要仿真那些东西?它能解决什么问题？
[答：Stanley]	For example, DC performance: INL,DNL FS error AC performance: SNR, THD,SFDR to evaluate ADC in your system requirment. thanks!	[2005-3-10 15:23:29]
[问：lwsar]	对于100MHz采样率，14bit的ADC，模拟地和数字地是同一平面还是单点接地比较好。另外电源呢？
[答：Daniel]	connect them as the same plane based on our experience before, but power should be separated to prevent crosstalk.	[2005-3-10 15:23:37]
[问：lwsar]	请问1Gsps的ADC使用哪种时钟方案，有没有具体的芯片。
[答：Daniel]	We recommend you to use National"s PLL to get the frequency. There is no single chip to provide 1GHz clock. Besides, the input clock of our ADC is differential input, not single ended.	[2005-3-10 15:24:54]
[问：Nickwu703]	什么是(IMD)? ADC需要注意这个参数吗?
[答：Stanley]	imd is Intermodulation Distortion. Any complex signal contains components at several frequencies simultaneously. Non-linearity in the converter’s transfer function will not only cause distortion of a pure tone; it will also cause two or more signal frequencies to interact and produce modulation products. When this happens, the result is called intermodulation distortion (IMD).	[2005-3-10 15:25:32]
[问：leonliu]	adc and dac的analog gnd and digital gnd在layout时要做区分吗？
[答：Daniel]	Depends on your application and speed. You can look at our Analog University, and there is an article to discuss about layout of ADC application system.	[2005-3-10 15:26:02]
[问：starluck]	请问我的ＡＤ采样速率很高，达５００ns,输入电压０～３.３v,输入信号只有毫伏级，能否建议一种放大器能满足条件
[答：Stanley]	you should consider settinng time: The combined settling time for an op amp and ADC for a full-scale step input to within 1 LSB must be less than the ADC’s specified sampling rate. here is our AMP for your reference, it is LMH6550	[2005-3-10 15:27:54]
[问：ty010496]	hi, can you give some tips on how to design the application board for such a high accuracy adc?
[答：Daniel]	You can look at one presentation file in our Analog University, and it has a richful layout and board level design guide. I recommend it to everyone who has interest in ADC application.	[2005-3-10 15:30:13]
[问：jasonfuaa]	Do Σ-ΔADC converters have any shortcomings compared with other ADCs?Thanks a lot.
[答：Daniel]	It"s very good and accurate, but the conversion speed is very low. So, you can not use it in any application.	[2005-3-10 15:31:42]
[问：jasonfuaa]	如何解决电源50Hz的干扰?采用带阻滤波方法能行吗?
[答：Daniel]	You can do it with filter, but most of the case, you need to resolve at power module side, not from ADC surrounding circuits.	[2005-3-10 15:32:45]
[问：hugoshiuaa]	目前segma-delta ADC最高可做到几bit?
[答：Stanley]	it can reach up to 24bit now	[2005-3-10 15:32:46]
[问：tudan]	How do you define the SNR and Input Dynamic Range in ADC Spec. Is there any relationship between them?
[答：Daniel]	To prevent to select an over-spec ADC, I"ll suggest to calculate the smallest signal and biggest signal in your system so that we can count the Dynamic Range. From the dynamica range you get, you can select an ADC which can meet your requirement. There is one foil to discuss about this question in "ABCs of ADC", National"s Analog University.	[2005-3-10 15:35:07]
[问：jasonfuaa]	怎样能够解决小信号的干扰问题？
[答：Stanley]	here is the list for you: ADC clock reference voltage input cuicirt thanks	[2005-3-10 15:35:32]
[问：ecnanjing _EBY7E]	DAC的线性度可以通过什么方式修正？
[答：Daniel]	If you want to correct it outside DAC, then it"s very tough. Or, you can choose another DAC.	[2005-3-10 15:36:01]
[问：ty010496]	how to measue the DNL,INL of the adc?
[答：Daniel]	You need to use an accurate signal generator and exact power input to check with sine wave and triangle wave. So, we can find the DNL & INL.	[2005-3-10 15:37:17]
[问：ty010496]	What is decimation in Sigma-Delta ADC?
[答：Stanley]	One of the hardest concepts of delta-sigma converters to grasp is how a one bit modulator output is converted into an 8,12 or 16 bit output word. To achieve resolutions of greater than one bit, the modulator output must be decimated. Through Decimation, time may be traded for increased resolution	[2005-3-10 15:38:27]
[问：hugoshiuaa]	对传感器的非线性如何进行补偿和校正?
[答：Daniel]	You can do it in Analog Domain (before ADC) or in Digital Domain (after ADC). It"s easier to handle it at DSP or MCU side. Besides, you need to measure the real non-linarity of your sensor, so that you can handle it after ADC.	[2005-3-10 15:38:59]
[问：leonliu]	请问INL DNL具体是指什么指标！
[答：Stanley]	INL:Integral Non-Linearity Error DNL:Differential Non-Linearity Error	[2005-3-10 15:39:53]
[问：bluenotes]	For a Engineer who"ll graduate from college this summer and start to work, which choice is better for him between discrete-time and continuous-time sigma-delta technique?
[答：Daniel]	You should master these two architecture, and pros and cons of them. Sometimes, your boss or professor will ask you to do it this way because of process or cost.	[2005-3-10 15:40:36]
[问：hbli]	请问你们的Analog University怎么登陆？
[答：Stanley]	you can log on : http://www.national.com/AU/	[2005-3-10 15:42:36]
[问：fish272]	is crystal not equal to oscillator? 在ADC 中外接的是晶振吗？是不是晶振的信号充当采样信号对输入模拟电压进行采样？
[答：Daniel]	They are different components, and you can send output of oscillator to ADC as clock input.	[2005-3-10 15:43:10]
[问：jasonfuaa]	一般的数模转换器在不加运放与电压满足情况下，可否驱动变频器或伺服驱动器？
[答：Stanley]	You should add an amp to increase input current for your application.	[2005-3-10 15:45:02]
[问：luzhenpo]	请问在相同的分辨率和采样速率下不同的转换原理的adc有区别吗？
[答：Daniel]	Yes, there are some differences. For some reasons, one may cost up than another architecture. So, we should trade off at quality and price confliction.	[2005-3-10 15:45:18]
[问：arbil]	从市场应用来看流水线结构和西格码德尔他结构的AD哪个更有发展前景；而整个AD/DA领域的技术、市场、地位将来有多大和什么样的发展空间？对IC设计工程师而言，投身AD/DA领域的风险和前途如何？
[答：Daniel]	These two architecture should be applied to different application, so it"s very hard to say which one is better than the other.	[2005-3-10 15:48:46]
[问：xulei]	请谈一下噪声特性
[答：Stanley]	here is some noise resource you can consider when you design: Inadequate Supply Bypassing Inadequate VA - VDR* Supply Decoupling Noisy Components/Conditioning Circuitry Quantization Clock Output to Input Coupling	[2005-3-10 15:49:09]
[问：m9002008]	请问DAC的输出若有glitch, 对系统会有何影响? 该如何降低DAC output的 glitch?
[答：Daniel]	Is this DAC desinged by you?? Or do you just use our ADC?? Probably you have to look at your power and ground layout. Or you may need to provide a clean power to DAC.	[2005-3-10 15:49:53]
[问：chlfatso]	AD转换器的原理一直没有质的变化,提高的只限于精度,抗噪性,转换速度吗?
[答：Daniel]	We can use the same architecture to improve accuracy and speed, but we need to change to other architecture when we reach the limitation of it.	[2005-3-10 15:52:25]
[问：m9002008]	要做一个由音频信号转化为数字信号的电路应该用什么样的模块?
[答：Stanley]	you can choose a decode module for your appliation.	[2005-3-10 15:52:50]
[问：fingure]	ADC and DAC used in oscillograph,speed is the important issue,which models are for oscillograph?
[答：Daniel]	National has the best solution for this application, and I recommend to use ADC08D1000 or ADC08D500, which are 8 bits and 1000MHz/500MHz sample rate ADC.	[2005-3-10 15:56:37]
非在线问答：
[问：]	ADC DAC 是不是一定要接MCu?
[答：]	Not exactly, people can use FPGA, DSP or CPU to handle those digital data.
[问：]	What application is more applicable for sigma-delta A/D?
[答：]	High accuracy but lower speed.
[问：]	可不可以用MCU控制采样频率。比如达到n个模拟输入通道分别不同的采样频率
[答：]	Yes, you can use National's ADC78H90 for 8 channel inputs and use MCU to control the channel through serial interface.
[问：]	在各种应用场合选取各类型ADC的原则是什么？
[答：]	Consider channel number first, and then calcaulate the bit resolution from SNR of your application. Then, thinking about the sample rate or conversion rate. Finally, we can look at other parameters.
[问：]	pipelined ADC中各级子DAC采用电容结构时，如果工艺产生偏差，致使电容失配，那么级转换电路的输出变化，对ADC的影响很大，如何解决？
[答：]	I recommend you can have a talk with your boss or professor, and it may not be caused by design only, but also from process parameter. If you need to simulate the result, you should simulate after you finish the layout of your architecture.
[问：]	A/D转换需要注意什么主要问题？
[答：]	system design or designing an ADC. If system design, I suggest you to look at our presentation file in National University. There is one file to discuss about the application design, especially to discuss about placement and layout.
[问：]	现在精度最高时多少？
[答：]	Technically can to reach to 30bits, but commercial products are about 24 bits.
[问：]	我较为关心转换精度与转换速度及成本的合理组合问题。谢谢。
[答：]	Then, I recommend to look at your input signal first. If you're concerning about price, then do not choose some ADC with over spec, like choosing 12bits ADC but you only need 10bits.
[问：]	模拟数字转换技术的发展趋势与最新进展.
[答：]	Higher speed, higher resolution but smaller package and power consumption.
[问：]	数模转换的方式有多少种？
[答：]	At least 6 as I know, and we'll discuss some of them at the coming on-line seminar.
[问：]	Please introduce the application of DAC in soft radio.
[答：]	Gerernal case, it's used in tramitter side and you can PA together with DAC to implement it.
[问：]	高速ＡＤ需要高速放大器吗？
[答：]	Yes, and high speed OP Amp is placed in front of ADC.

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