如何選擇DA?

問：windytj] DAC晶片選擇時其轉換速度與精度如何權衡才能得到最便宜的晶片？謝謝

[答：LiaoWS] The simplest way for you is to give ADI a call, we can select one for you. Our contact way is 800 810 1742.  [2003-10-30 11:45:39]

[問：hobodom] 請問專家，在D/A應用過程中，内部參考電壓和外部參考電壓優劣怎樣？應該如何選擇？對無雜散動态範圍得影響是什麼？

[答：Mariah] Generally speaking,internal reference is not good as external reference. If the specification which can be get from the datasheet is not good enough, you should use an more accurate reference. The main parameter for reference is the initial accuracy,temperature drift,noise etc. The DC performance of reference will not influence SFDR while AD performance will influence SFDR more.  [2003-10-30 11:46:49]

[問：Lawson_jian] 請問，低通濾波于A/D和D/A之間的比對要注意那些問題

[答：LiaoWS] Pay attention to the impedance match, the signal bandwidth, voltage range.  [2003-10-30 11:47:29]

[問：lwbence] 對DA而言，一般場合是用内部參考源還是外部參考源？如果是外部的，一般電源晶片的輸出可以嗎？

[答：LiaoWS] Normally, you can use internal reference. If you want to use external reference, please don"t use the power supply parts, you can consider our ADRxx series of reference parts.  [2003-10-30 11:49:10]

[問：hardyye] dac 的精度于速度有什麼關系

[答：Theresa] There is no direct relationship between accuracy and speed of a DAC.

Current output DACs are much faster settling in ns in contrast to voltage output dacs, settling in ms. 

Both types are available with 16 bits of accuracy.  [2003-10-30 11:49:37]

[問：快捷方式] 據說現在市場上有18bit以上的DAC，不知貴公司有沒有這樣的産品？若有能否給一些介紹？

  順便問一個不相關的問題，在一篇文章上看到ADI有一款運放AD8751，但在ADI首頁上看不到這個型号，這是怎麼回事？

  謝謝！

[答：Wayne] Normally for DACs with resolution higher than 16 bit are audio DAC with Sigma-delta technology. AD185x is good which can support various sample rates.

Could you contact with 8008101742 for the amplifier part# you mentioned ?  [2003-10-30 11:49:41]

[問：982441] 現有的D/A轉換器轉換速率最快能達到多快？

[答：LiaoWS] For ADI, the fastest is 500MSPS. They are AD9782/4/6.  [2003-10-30 11:49:47]

[問：wffae] 用多通道D/A輸出時，如何避免在同時工作時，每個通道受其它通道的幹擾？

[答：Albert] There are generally two mechanisms contributing to crosstalk. The first is internal to the device relating to its internal design. The component vendor generally looks after this crosstalk mechanism minimizing as much as possible in the layout phase of the design by incorporating isolation between channels, avoiding interraction of the analog and digital sections and paying attention to clock distribution etc,.

The second mechanism relates to the use of the product in the end user application. Paying attention to layout, isolating channels with analog ground and good decoupling of the supplies will help minimize crosstalk.Its also important when using fast digital logic in the interface to avoid overshoot and undershoot on the signals as this couples acorss the device effecting performance. [2003-10-30 11:50:24]

[問：chenpld] ad和da連接配接起來時，在給定的采樣速率和量化比特數時，決定系統的信噪比的關鍵因素?

[答：Jing] You can refer to this equation:

1. SNR [dB] = 20 x log (2^(n-1) x √6)

2. Approx = 6.02n + 1.76

The ideal SNR is affected by the resulotion. But in the real world, you should minimize the noise such as EMI and be aware about the layout and the decoupling circuit. [2003-10-30 11:50:37]

[問：candid] 請問設計pcb時，都有哪些措施降低噪聲對dac的影響？

[答：MelConway] Use good high frequency decoupling capacitors [multi layer ceramic etc. connected with the shortest possible leads directly to the DAC supply pins and grounds.

Use single point grounding of separate Analog and Digital grounds.

Use ground planes under and around the DAC.

Do not route any digital signals near or parallel to any analog signals.

Shield or decouple any high impedance nodes.

Use filtering on the output and reference inputs if necessary.

Minimize all impedances and resistances.

Minimize over- and under-shoot, and ringing on digital lines. Use line matching and termination if necessary on high speed lines. Limit slew rates on digital signals.

Limit siganl and reference bandwidths.  [2003-10-30 11:50:38]

[問：drly] 您好！請問應用在微小型系統上的數模轉換器都有什麼型号？尺寸是多少？以此設計聲頻信号發生器還需要注意什麼？

[答：William] You can look at the 16-bit products for highest accuracy.  AD5570 would be well-suited for this application.  It"s available in 16 pin SSOP package.  [2003-10-30 11:51:31]

[問：falling74] 請問專家，DAC的數字端和模拟端的地怎樣連接配接時，效果比較好

[答：Wayne] A good PDF book for your reference: http://www.analog.com/technology/amplifiersLinear

/training/sensorSignal.html  [2003-10-30 11:52:15]

[問：qiangnet] 能否推薦一個10M/8BIT的并行D/A轉換器？

[答：Mariah] AD9709 8bits, 125MHz,parallel D/A  [2003-10-30 11:54:38]

[問：q31488] 能問問光驅或影碟機裡數模轉換器的型号、功能嗎？

[答：Wayne] Could you contact with ADI toll-free phone [phone] for details ? we need to know channel#, resolution#, and interface your system requires.  [2003-10-30 11:55:14]

[問：haoyangd] 請問在Delta-Sigma DAC中主要的技術名額常常是SNR,THD,GainError,等等，而不是常見的DNL,INL,為什麼？另外這兩種名額之間有沒有可以替換的公式？謝謝。

[答：LiaoWS] The reason is that Sigma-Delta DACs maily used in audio, which doesn"t care the INL/DNL DC specs. There is no equations among them.  [2003-10-30 11:55:19]

[問：wistful] ADV7189何時能批量供貨?

[答：Wayne] ADV7189 schedule to production in November 2003.  [2003-10-30 11:56:22]

[問：姚黎鋒] 請問：目前的DAC晶片所能适應的環境溫度在哪個範圍内？

[答：LiaoWS] ADI can provide parts in almost all temp range, from 0-70 to -55-125 degree. Please refer to their datasheets.  [2003-10-30 11:56:34]

[問：lxl9726] 請問A/D、D/A的轉換精度現在最高是多少位？謝謝！

[答：LiaoWS] Both 24-bit accuracy.  [2003-10-30 11:57:17]

[問：weijie_lee] ADI有沒有串行接口的大于12位的DAC晶片？

ADI的晶片為什麼好多都沒有庫存？

DAC的方式哪一種最先進？

[答：William] AD7846 etc. fits your requirement.  One cannot say that one structure is more advanced as each type of structure is designed to optimize certain specifications.  We do try to provide fast delivery of our products to customers.  Many of our products are now available without a long lead time.  [2003-10-30 11:57:51]

[問：thep

rimegod] 講的非常好。

為了使輸出平滑，數模轉換器的輸出是不是需要接一個電容，那麼這個電容應該怎樣選擇呢？謝謝！

[答：Mariah] Please reference the evalution board of the dedicated DAC part.  [2003-10-30 11:58:58]

[問：join-lin] 我們在選擇D/A器件時，對精度的選擇要如何判斷？

[答：LiaoWS] It is decided by youy system requirement. For example, some system needs 16-bit resolution, but for some systems 8-bit is enough. You can discuss your applicaiton with us via 800 810 1742.  [2003-10-30 11:59:02]

[問：漢山] 在MCU控制的錄放音系統中，如和選擇A/D和D/A？謝謝

[答：William] Depending on your performance requirement, you can choose either the mono codec AD73311 or stereo AD73322.  [2003-10-30 11:59:33]

[問：kyt1999] 對與DA轉換器的精度一般如何計算和選擇,對DA轉換器布線是數字地和模拟地是否必須絕對分離,單點相連?

[答：Wayne] DAC accuracy depends on DAC architecture and the actual sample rate you"re using. Basically you need to know what"s the SNR requirement you must leave for DACs, then the effective resolution can be calculated by ENOB=(SNR-1.76)/6.02.

Single ground should be used for DAC as it"s mixed signal chip. You can refer to below book:http://www.analog.com/technology

/amplifiersLinear/training/sensorSignal.html  [2003-10-30 12:00:18]

[問：nilibi] 精度和分辨率的差別

[答：LiaoWS] Jingdu is accuracy, Fenbianlu is resolution. Resolution means how many bits, accuracy means INL/DNL specs.  [2003-10-30 12:01:40]

[問：TSZ889] 請問DAC适用于頻率高的電路嗎

[答：LiaoWS] Of course. We have TxDAC series of DAC used in base station and handset.  [2003-10-30 12:02:21]

[問：jikjikjik] 有那些比較通用的8位DAC産品?價格如何?

[答：William] AD5424/5/6 etc. are all 8-bit DAC.  Please check with our distributor regarding its price as it is related to the quantity.  [2003-10-30 12:03:34]

[問：guorock] 一般AD公司的晶片承受過載的能力如何？

10000個g的加速度能承受嗎？

[答：LiaoWS] Our MEMS parts can tolerate 3500g. But for normal parts, they cannot tolerate 1000g.  [2003-10-30 12:03:35]

[問：jikjikjik] 請問,什麼DAC/ADC是多通道的?

如何選擇此類器件?

[答：Wayne] We"ve very big family of multi channel DAC/ADC like AD538x, AD539x, AD7689/7998...... Also we"ve multi channel ADC and DAC and MCU integrated chip ADuC8xx.

If you need to select a proper part, please call 8008101742 to give your system requirement including resolution, sample rate, interface....  [2003-10-30 12:03:37]

[問：lijianhong] How to use D/A converter to get a current output from -10mA to 10mA? IS it need a V/I converter such as AD694?

[答：Albert] The AD694 will only allow unipolar output current of o to 20mA.

A more efficient and cost effective method of generating a bipolar current is to use a bipolar voltage output DAC in conjunction with an external amplifier configured as a Howland current pump to generate the bipolar current control.  [2003-10-30 12:03:38]

[問：smx

64098] 請問D/A本身所代運放的驅動能力有多大？

[答：Theresa] The output of the op amp is low output impedance.  [2003-10-30 12:03:42]

[問：0206

47319] 請問使用了數模轉換器的電路在電磁相容試驗中有什麼需要注意的嗎？

[答：Gary] The digital Inputs and Outputs can be the cause of a lot of EMI, this is true for transient discharges to enter a piece of equipment, and for interfering signals to escape, either by conduction of spurious signals on the I-O lines or by radiation from the I-O cable. Because of this, the EMC performance of the I-O port is crucial to the EMC performance of the entire package.

For succeptibility, You should check that the output voltage goes to the correct expected value, this will ensure that the interface is robust. Also check how much of the interference is being coupled onto the output, and where it is getting coupled through. [2003-10-30 12:03:54]

[問：stick] 設計低位數（4位），高速（250M以上）的DAC一般采用什麼結構？

[答：Albert] Current Source based DAC for speed.  [2003-10-30 12:04:28]

[問：cby9

81541] 高檔計算機數字音箱裝置使用什麼類型的D/A轉換器比較好？

[答：William] Our AD1885 etc. are used very widely as the SoundMax AC97 codec.  [2003-10-30 12:04:35]

[問：samire] SFDR,THD和速度之間的關系如何處理?因為視訊應用的高速CMOS DAC的SFDR和THD都較差.有何好的解決方法?

[答：Wayne] You may find proper product in ADI catalog, like ADV7123 DAC, ADV7171/ADV719X/ADV73xx as video encoder.

You can call 8008101742 to give details of your application, our engineers will help you on part selection and design support.  [2003-10-30 12:07:21]

[問：648919] Σ?Δ ADC的規格說明常常假定 某一輸入時鐘頻率，進而也就規定了 采樣速率。如果使用的時鐘頻率高或低于規定值，那麼我能可靠地使用這種轉換器嗎?

[答：LiaoWS] Normally, there is a clock range for the parts. Use the clock in this range should be no problem.  [2003-10-30 12:07:23]

[問：yang

yang23] 高品質的音頻輸出 考慮做成Hiend推薦采用那種dac好？ 請告知

[答：William] AD1955 is regarded as the industrial performance leader for audio DAC.  ADI has many audio DAC which are used in hi-end audio.  Please refer to our selection guide for details.  [2003-10-30 12:07:57]

[問：qin] 如何考慮高速DAC的接地?多少位的DAC需要認真考慮?

[答：Mariah] Please reference the book "High Speed Design Techniques" which can be downloaded from ADI website. www.analog.com  [2003-10-30 12:08:28]

[問：johnling] 請問音頻DAC有哪些最新型号?

[答：William] AD1955 is the latest one.  AD1853 is also quite popular.  [2003-10-30 12:09:39]

[問：johnling] We design digital mixer, which kind of DAC you will recommand to us?

[答：LiaoWS] Please let us know your bandwidth, SFDR, SNR requirement. Then we can help you on your case. Please contact [email protected] or the toll-free number 800 810 1742.  [2003-10-30 12:11:33]

[問：wffae] 請問目前有沒有不需reference voltage D/A産品？thanks!!!

[答：Mariah] What do you mean no reference voltage D/A? Does that mean no external reference voltage? We have a lot of parts with internal reference such as AD667,AD767,AD7233 AD7243 etc.  [2003-10-30 12:11:50]

[問：zjg18] 請推薦最常用的12位串行dac/adc

[答：Wayne] If you use MCU, I"ll suggest you use ADuC812/831/832/841/842, which integrates 8051 MCU plus 12 bit ADC with MUX, 12 bit DAC.

We"ve big family for 12bit ADC, like AD78xx, and 12bit DAC as well like AD532x. It depends on what sample rate you need as well.  [2003-10-30 12:12:52]

[問：ljp] 什麼是量化噪音?不同分辨率的DAC,其量化噪音有何不同?

[答：LiaoWS] quantilization noise is inherent to the converters. For different DAC, the quantilizaiton noise is different. Please refer to page 54 of the presentation.  [2003-10-30 12:16:01]

[問：roa

mingsky] DAC的轉換時間取決于哪些方面，ADI公司的産品最短可以達到多少時間，具體有哪些型号，thanks！

[答：LiaoWS] It is decided by the architecture. Our fastest is 500MSPS, they are AD9782/4/6.  [2003-10-30 12:17:46]

[問：lucawrj] 請專家談談影響D/A轉換精度因素和相應采取的措施

[答：MelConway] The factors are internal and external.

Internally architecture, fab process, and design all contribute to accuracy. Accuracy may also be improved by trimming [laser or other means] or calibration. Low offset output amplifiers are necessary.

Externally the Reference must be carefully selected to give required performance over temperature [ppm/oC]. Minimize temperature excursions. Use high quality components with low TC Temperature Coefficient.

Accuracy depends on Resolution, higher resolution DACs are typically [but not always] more accurate. Choose a DAC with INL Integral NonLinearity of 1LSB Least Significant Bit or smaller for best linearity. beware of INL [also known as Relative Accuracy] which is specified in percent % of Full Scale - older DACs may have been specified in this way but newer parts do this often to hide poor accuracy.  [2003-10-30 12:17:58]

[問：wffae] 請問：有種産品需8Bit D/A,但輸出容易受電源的紋波影響，有沒有一種不受電源紋波影響的D/A晶片啊？

[答：Wayne] AD530x/533x can be good choice. But, all ICs can be affected by power supply ripple. Therefore, you need always choose good DC/DC or LDO (ADI has good products ADP3xxx). Also, you need to do good power supply de-coupling according to general rules, or the datasheet of the DACs. For details of the rules, you can refer to: http://www.analog.com/technology

/amplifiersLinear/training/sensorSignal.html  [2003-10-30 12:18:07]

[問：dengxy1960] 目前高校實驗一直沿用0832,請推薦幾款物美價廉的DA晶片

[答：Mariah] AD5300,AD5301,AD5330,AD5331 etc.

You can dial the toll-free number 800-820-1742 to get ADI products short form.  [2003-10-30 12:18:51]

[問：andrewpei] 請問在選擇高精度的DAC時，與選擇普通DAC有何不同的地方，應着重哪些技術名額。另外，并行輸入口和串行輸入口的DAC，哪一種抗噪聲能力更好一些，對于數字IO，應該采取些什麼隔離措施呢？謝謝

[答：William] The high accuracy DAC will of course have better specifications.  One should look at the DC specifications such as offset, gain error, temperature drift, DNL, INL, etc.  Parallel or serial I/O won"t make much difference in terms of resistance to noise.  However, many people found parallel port to be easier to use because the speed is much lower.  Digital lines should be kept as far away from the signal line as possible and separate ground should be used.  [2003-10-30 12:19:12]

[問：tugang0731] 你好：我曾經使用過adc0809和dac0832,這為兩種比較常用的晶片，但現在我想用一些高精度的模數轉換元件，請問該選用什麼型号的比較好！

[答：William] Depending on your application, please refer to our selection guide based on your accuracy needs.  [2003-10-30 12:20:33]

[問：呂毅] 要實作高精度的數摸轉換，最值得注意的地方除了好的電源和對模拟信号的保護外還有什麼啊

[答：Wayne] At first, you need high performance DAC,

then except power supply, and protection, you need to follow other ruls of PCB layout. You can refer to below book for the rules: http://www.analog.com/technology

/amplifiersLinear/training/sensorSignal.html  [2003-10-30 12:20:50]

[問：qin] 在PCB Layout時如何對産生噪音的元件如電容,開關電源,磁性元件等元件進行屏蔽以增加動态範圍?這種屏蔽如何和地線相連?在什麼地方相連最好?

[答：LiaoWS] You can place them far away from your parts. And shield them if necessary. The shielding should be connected to AGND. The GND should be connected at the power supply as the common one.  [2003-10-30 12:21:37]

[問：youzidu] 請問如何更好的選擇AD公司的sigma-delta 數模轉換器？

[答：William] Please tell me specifically what application in which are you interested.  Sigma-delta DAC are used mainly in audio.  If that"s the application you need, then DNR and THD are the most important specifications.  [2003-10-30 12:22:02]

[問：劉潤秋] sip及iic接口傳輸距離是多少？

[答：LiaoWS] It is decided by the wires you used. And should be decided by your system design.  [2003-10-30 12:22:32]

[問：dairlom] 先生你好：我現在正打算做一個8位的D/A轉換，要求的較高線性度；速度可以不用太快（10K左右）；能直接電壓輸出；輸出極性有單級性和雙級性兩種。謝謝！

[答：Mariah] AD5530 12bits,voltage output, bipolar output  [2003-10-30 12:22:47]

[問：johnzhou] DAC輸出不穩定經常出現跳變（跳到峰值），該如何防止這種情況發生。

[答：William] This is not a normal behavior for precision DAC.  You can try reducing the load current by adding external buffer.  [2003-10-30 12:23:03]

[問：samire] 高速DAC在PCB布局設計時需要考慮那些因素,以降低寄生參數的影響?

[答：LiaoWS] How fast is your DAC and data lines. One common way is to use multilayer layout and use more gounds.  [2003-10-30 12:23:23]

[問：lhg100] DAC 與 PWM做的電流輸出在應用的差别？？？（有些晶片如PIC自帶多路PWM,這樣很有價格優勢）

[答：Jing] You can refer to our ADuC831/2/4. There is DAC output together with PWM output. The PWM can be configured as a Sigma-Delta DAC and other application.  [2003-10-30 12:23:27]

[問：haoyangd] 我想繼續問DeltaSigma DAC的名額的問題：一般情況下，DeltaSigma DAC是應用在音頻領域，但是我知道ADI有一個産品AD421是應用在工業控制領域，它的名額就是以INL提出來的，那麼在設計時是如何測試該名額的呢？我在做類似的設計，但是對如何測試DeltaSigma DAC的INL名額有疑問，特此提出，希望能給予回答。

[答：Albert] INL or integral non linearity basically tells the user the error between the actual and ideal output for a D/A converter.

From the design we can generally predict at which codes the worst case INL occurs and test for these as part of the final test.

Therefore  in testing a specific code is loaded to the DAC and the output voltage measured, the difference between the measured and the ideal after taking out the offset and gain error results in the INL error and this is generally specified in lsbs or percentage of fullscale.  [2003-10-30 12:24:14]

[問：zhai

shenghua] 您好，我正在使用貴公司的12-Bit, 125MSPS DAC AD9752,請問，在電路設計中有什麼需要特别注意的地方？

[答：LiaoWS] The simplest way for you is to refer to the evaluation board schematic and layout. any technical support needed, feel free to contact 800 810 1742 or [email protected]  [2003-10-30 12:24:20]

[問：cobuild] 我想選用一種數模轉換器，要求工作電壓為+5V，12位并口電壓輸出，兩路或者四路輸出，請問ADI公司的産品中有哪些可以選用？價格分别是多少？

[答：Wayne] AD5342/3 (12bit, dual DAC), AD5344 (QUAD 12bit DAC) is good choice. For price, please contact with local ADI office, or ADI distributor.  [2003-10-30 12:24:54]

[問：wistful] 在進行DA轉換時,器件已經標明,如何通過布線來提高信噪比?

[答：Mariah] The best way is to reference the PCB layout of the evalution board of the dedicated part.  [2003-10-30 12:25:13]

[問：lyz_b

lue_sky] 在國内，有很多像我這樣經驗很欠缺的技術人員，在選擇DAC時，不知如何選擇，對很多參數了解得不夠深刻，如何緩解這些問題？

[答：LiaoWS] OK, you can call us by 800 810 1742, or send mail to [email protected]. We will be very happy to help you.  [2003-10-30 12:25:15]

[問：candid] 設計電路闆時，如何才能保證d/a，a/d的精度不受影響？

[答：Wayne] There"re various rules that you need to follow:

http://www.analog.com/technology

/amplifiersLinear/training/sensorSignal.html  [2003-10-30 12:25:38]

[問：ljp] 16位30MSPS的DAC,DNL為什麼隻有14位?14位的DNL是否意味着是非單調的?

[答：William] A 14 bit DNL in a 16 bit DAC means the part is NOT monotonic.  Montionicity requires DNL to be within 1LSB.  To achieve both high speed and accuracy is difficult.  DAC with this kind of speed is usually used in communication system.  Monotonicity is usually not required in this application.  [2003-10-30 12:26:01]

[問：662135] How about D/A transfer resolution?

[答：Mariah] What does "TRANSFER" resolution mean?  [2003-10-30 12:26:22]

[問：chen

xinyu009] 選擇數模轉換器有不有更快捷的方式

[答：LiaoWS] Call the toll-free number 800 810 1742. It will be fast, and we have selection guides ready for you, we can send them to you if you can let us know your address.  [2003-10-30 12:26:30]

[問：chen.wei] 有用于高清晰度電視系統的DAC嗎，是什麼型号？

[答：Wayne] I think you means video encoder, then we"ve good performance parts like ADV7195/6/7 supporting HDTV. We"ve also ADV73xx which support both SDTV and HDTV.  [2003-10-30 12:27:36]

[問：grey_

yz1949] 我正在用FPGA控制DAC0832。産生正弦信号采用查表法，但是總是在過零點的時候有較大的毛刺，請問是0832内部的問題嗎

[答：William] DAC0832 is a rather old part.  I suspect this is caused by switching of the internal driving circuit.  [2003-10-30 12:28:00]

[問：wffae] 為了保證高精度，在PCB layout 方面應特别注意些什麼？thank!!!

[答：LiaoWS] Design with good decoupling, good grounding method, use the right power supply. And make sure to refer to our evaluation board schematic and layout. For technical support, call 800 810 1742, or send mail to [email protected]  [2003-10-30 12:28:27]

[問：SHIFENG] 選擇數模轉換器需要考慮哪些外部因素？外部環境對器件本身有沒有影響？

[答：Jing] You should pay attention to the environmental temperature and the EMI . It"s will bring the  temperature drift to the device .  [2003-10-30 12:30:42]

[問：kzw] 除了sigma-delta型的DAC之外，還有什麼型的DAC?

[答：William] There are others such as R-2R (sting DAC) and voltage divider type.  [2003-10-30 12:32:19]

[問：tuo

lang2000] 在數模轉換器中其轉換頻率和器件的采樣周期是否相同，在設計D/A變換的時候，怎麼才能避免EMI的問題

[答：Jing] It"s different. You should pay attention to your PCB layout such as decoupling and seperate the analog from the digital GND etc.  [2003-10-30 12:32:46]