LTZ1000原设计者对基准的一些看法

chinapp

准确说应该是，LTZ1000手册电路原设计者对基准的一些看法，因为从原文我只能得到这些信息，Bob Dobkin到底是不是LTZ1000的设计者没有证据，
这是国外一个论坛偶然看到的，原文转过来，作为大家参考，以后有时间会考虑翻译一下：（背景是该网友同Bob Dobkin电话交流了基准的一些问题，他把Bob Dobkin的一些看法发了出来。

“
Hello fellow forum users,

I just finished with a telephone conversation with Bob Dobkin, and he was short on time, so I was not able to get all of the answers to every question I [and we] had, but here are the ones I was able to get:

1) [FYI]:  The applications circuits in the LTZ1000 data-sheet and other ap-notes were designed by Bob Dobkin, not Jim Williams.

2) Regulation in the LTZ1000 is more about controlling the power rather than controlling the voltage.  If you accurately control the power, voltage stability will be achieved as a by-product.

3) The LTZ1000A has a different die attach than the LTZ1000, but they are both isolated quite a bit from external lead stress.  Both of them will respond a small amount to lead stress, but the 'A' version if far less susceptible to this.  Bob said that this can show up as a drift in output voltage with changes in barometric pressure.

4) It's been 20 years, so he didn't know the exact numbers, but Q1 is only rated to a few hundred micro-amps of collector current.  [This means my single-resistor idea will *not* work! -- back to the original circuit from the ap-note!]  Q2 will have a max rating of around 1mA, and the Zener can take quite a bit more.

5) They *could* make a model for LTspice, but the temperature effects are very difficult to simulate, and the market need is not large enough to support the development effort [my words].  He said the best way is to build the circuit and test it out in real life.

6) After telling him that I wanted a voltage transfer device, he said a better way might be to use [at least 6] LM399's in parallel [like the Bob Pease idea].  He said that the burn-in procedure would be to operate these in an oven set to 125C for 2 weeks, which would be equivalent to 1000's of hours of normal operation.  Any LM399's that are drifting too much after that can be replaced [i.e., you burn-in more than you need, and select the best units for the array].  The LM399 is much more sensitive to board stress than the LTZ [because the LTZ has a special mechanical arrangement in the die mount]-- so the LM399 should be mounted off of the PCB a little bit to allow for this.  The long term stability of the array of LM399's will be directly related to the power required to run the heater-- and this can be minimized with insulation-- the more the better!  The LM399's do not age when they are turned off, and have almost no hysteresis-- so keeping the reference *off* until a few hours before you need to use it [and/or calibrate it] is the best way to keep the long-term drift minimized.

7) Note that for LM399-based designs, the slots in the PC board [plus a lot of insulation top and bottom] make sense-- Bob said that the less power the heater requires, then the more stable the output voltage will be.  So, in this case, the slots [plus insulation] are helping with this.  Oh-- and he also said that the LM399 should be run at about 1mA of Zener current for best stability.  The more stable you can make the Zener current, the more stable will be the output voltage.  He said that there is about 1uV of voltage change for 1uA of current change.

8: All voltage references *do* age faster at higher temperatures.  So, since the LTZ1000 can be run about 10-deg-C lower than the 'A' version, it will have lower [about 1/2] long-term drift than the LTZ1000A under otherwise identical conditions.  [But, the 'A' version has *other* differences that are positive-- my words.  There are other sources of drift that the 'A' version is less susceptible to-- barometric pressure changes is one of them].

9) For the LM399 and both of the LTZ parts, he said a good burn-in routine would be to operate them at 125C [in an oven] for 2 weeks.  After that, you can cycle the power on and off 10 to 15 times at normal operating temperature, and this will get them to settle down.  This process should remove most of the initial drift that these devices exhibit.  [So, my initial guess for a burn-in cycle was pretty good-- there is nothing wrong with a burn-in 10 times longer than this.]

10) If properly insulated, an LM399 can have a ppm/K figure of between 0.1ppm/K to 0.2ppm/K-- the data sheet is *very* conservative.  [Note that the DMM manufacturers are not insulating these other than the plastic insulator that they come in-- they would benefit by better insulating the top and bottom of the LM399 to keep the heat in, and the heater power down.]

11) They are working on releasing more parts in the LS8 [8-pin ceramic LCC] package-- they should be coming out later this year.  Some of the parts will not fit in the LS8, and they will have to use a larger ceramic LCC for those.  He said the 1021 series will also be on the list of parts that will be released in LS8.

12) The ceramic LCC's have Kovar in them to get out of the package-- so, you don't get away from the thermal EMF problem, and these parts should be insulated from air currents [just like the TO-style packages] after they are mounted on the board.

13) The LTZ parts do not need to be spaced above the PC board like the LM399 does due to the unique mechanical de-stress design inside the package.

14) They will not be building a reference design for the LTZ part-- this is a niche product that does not warrant the development time.  [That does not mean that *we* cannot come up with our own reference design!  Let me think about this-- perhaps if there is enough interest, I can take the risk to do this...]

15) The TO packages are filled with *DRY AIR*-- not even nitrogen-only [so you would expect some degradation from this-- my words]-- but, Bob says that they don't have any parts that are degraded by this.

16) The LTZ1000 will use a lot more power than the LTZ1000A, so for battery operated circuits, it's best to go with the LTZ1000A, and insulate it to save power.

17) There is probably not a scenario where you can get zero-TC out of the LTZ-- he said you probably would have to operate Q1 at around 1uA, and that is not practical.

18) He said that it is not necessary to use the LTC2057, as the drift and noise of the Zener contribute far more than the LT1013.  Bob said that you could use almost any precision op-amp, and the drift would not be affected by much even by the less precise amps.  [I'm still going to use the LTC2057 anyway-- they are as cheap as popcorn, and have very little noise.  Since I *do* need a zero-drift amp in the follow-on boost circuitry, and it's more economical to keep the number of unique parts on the BOM as low as possible.]

19) The Zener in the LTFLU-1 is the exact same one as is in the LTZ1000.  He said that even though the exclusivity portion of the contract with Fluke is no longer in effect, they are not going sell these to the public because they don't want to anger a customer that buys millions of dollars in other parts from them.  Even if they did want to sell it to others, it has not been characterized and there is no data sheet-- so there would be a lot of work just to build that.  It's just not going to happen...

20) Bob said that he would join this forum, but he doesn't have enough time in the day to deal with what he already has to do-- so, it is not likely that he will participate.  He said that I can email him with any questions I [we] have in the future, and he will do his best to answer them.

That's about all we could fit in.  I hope that helps everyone-- it sure helped me a lot, as I was able to see that my "single resistor" design would not work.  Bob said the that the LTZ would probably not be destroyed by my circuit [because "the LTZ can take a lot of abuse"], but it still would not ever be reliable even if it did work in the laboratory.

I was furiously taking notes during the phone call, and so I may have missed a few things-- if I remember anything I missed I will post it.

Regards,
Ken

”

长风

各位论坛用户，
我只是完成了鲍勃道金的电话交谈，他很短的时间，所以我不能把所有问题都回答我[我们]了，但这里是我能：
1）[仅供参考]：在数据表和其他AP ltz1000笔记应用电路设计的鲍勃道金，不是吉姆威廉姆斯。
2）在规定更多ltz1000控制力而不是控制电压。如果你准确地控制电源，电压稳定性将达到作为一个副产品。
3）具有不同的管芯附着的ltz1000a比ltz1000，但他们都是孤立的不少来自外部的铅胁迫。他们都会有少量的铅胁迫，但A版如果这个敏感的少。鲍勃说，这可以显示出与大气压力变化的输出电压漂移。
4）已经20年了，所以他不知道确切的数字，但是Q1仅为额定几百微安培的电流。【这意味着我的单电阻的想法将不会工作！——从AP注回原来的电路！] Q2将有一个最大的评级在1mA，和齐纳可以采取相当多的。
5）*能* LTspice做模型，但温度效应的模拟十分困难，而市场需求不足以支持发展努力[我的话]。他说最好的办法是建立电路和测试它在实际生活中。
6）告诉他，我想要一个电压转换装置后，他说一个更好的方法可能是使用[至少6个]的[像lm399平行鲍勃皮斯思想]。他说，老化的过程会操作这些烤箱设置为125 2周，这就相当于1000的正常运行时间。任何的漂流lm399太多后，可以更换[即老化，你超过你的需要，并选择最佳的单元阵列]。lm399比的LTZ [板应力更敏感，因为LTZ有特殊的机械布置在模具安装]——所以lm399应安装在PCB的一点点，让这个。lm399的阵列的长期稳定性将运行所需的加热器的功率直接相关——这可以减少绝缘——越多越好！这是不是年龄lm399关闭时，几乎没有迟滞——所以保持参考*关*直到几个小时之前，你需要使用它[它]和/或校准是保持长期的漂移最小化的最佳途径。
7）注意lm399为基础的设计，槽在PC板[加很多绝缘的顶部和底部的]道理——鲍勃说，更少的功率加热器的需要，那么更稳定的输出电压将。所以，在这种情况下，槽绝缘[加]帮助这。哦——他还说，应该运行在约1mA lm399的最佳稳定性齐纳电流。更稳定的可以使齐纳电流，更稳定的将输出电压。他说，人们对于1uA电流变化的电压变化1uv。
8：所有电压参考* *年龄在较高的温度下更快。所以，自从ltz1000可以运行比' '版本低约10-deg-c，它具有较低的[ 1 / 2 ]长期漂移比ltz1000a在其他条件相同的情况下。【但是，' '版*其他*差异是积极的——我的话。还有其他来源的漂移，A版是不易——气压的变化是其中一个]。
9）对两lm399 LTZ部分，他说一个好的老化程序会操作它们在125 [烤箱] 2周。之后，你可以循环和关闭电源10到15倍，在正常的操作温度，这会让他们安静下来。这一过程应去除大部分的初始漂移这些器件表现出。【所以，我最初的猜测一个老化周期很好——有一个老化的10倍以上，这没有错。]
10）如果适当的绝缘，一个可以有一个对lm399 0.1ppm/k 0.2ppm/k- -数据表之间的数据ppm / K的数字是非常保守的。[注：数字万用表的厂家不绝缘这些比其他的塑料绝缘体，他们来了——他们会以更好的绝缘的lm399顶部和底部的保温效益，和加热器电源关闭。]
11）他们工作在LS8【8引脚陶瓷LCC ]包释放更多的部分——他们应该在今年晚些时候。某些部分将不适合在LS8，他们将必须使用较大的陶瓷LCC的。他说，1021系列也将对部分将被释放在LS8列表。
12）陶瓷LCC的伐在他们滚出去包的——所以，你不要离开热电势的问题，这些部件应与空气隔绝电流[就像风格包]后，他们都在船上安装。
13）


包。

长风

14）他们不会为LTZ部分建筑设计的参考——这是一种特殊产品，并不保证开发时间。[做
不是说我们不能拿出自己的参考设计！让我想想——如果有足够的兴趣，我可以冒风险做这……]
15）的包充满了* *——甚至没有空气干燥氮[所以你会期待一些退化从这个——我的话]——但是，鲍勃说他们没有任何部分是退化的。
16）第ltz1000会使用很多更多的权力比ltz1000a，所以对于电池供电的电路，最好去与ltz1000a，隔热节能。
17）有可能不是一个场景，你可以得到零TC的LTZ——他说你可能会操作Q1在1uA，这是不实际的。
18）他说，这是没有必要使用ltc2057，作为漂移和齐纳噪声的贡献远远超过LT1013。鲍勃说你可以使用几乎所有的精密运算放大器，和漂移不会受太大影响甚至由不太精确的放大器。[我仍打算使用ltc2057无论如何——他们像爆米花一样便宜，有很小的噪音。自从我在后续的升压电路做*需要一零漂移放大器，它是更经济保持独特的零件数量，对BOM的尽可能低。]
19）在ltflu-1齐纳是完全相同的一个是在ltz1000。他说，即使侥幸合同独一无二的部分不再有效，他们不会向公众出售这些因为他们不想激怒顾客购买数百万美元的其他部分的。即使他们想卖给别人，它并没有被其特征在于没有数据表——所以会有很多工作刚刚建立。这是不会发生的…
20）鲍勃说他会参加这个论坛，但他没有足够的时间去处理他所做的——所以，这是不可能的，他将参加。他说，我可以让他有任何问题我[我们]有没有未来，他会做他最好的回答。
这就是我们能在。我希望帮助所有人——它确实帮了我很多，我可以看到我的“单电阻”设计不工作。鲍勃说LTZ可能不会被我的电路[因为“LTZ可以采取了很多的虐待”]，但它仍然不会即使在实验室所做的工作是可靠的。
我拼命记笔记在电话，所以我可能已经错过了一些事情——如果我记得什么我想我将它张贴。

长风

试试看。

simon51

学习了

sssaaa

有意思。

chinapp

你这种自动翻译太蹩脚了，翻译不好的话很容易误解原文的意思

switch131

似乎谷歌的全文翻译还不错

shichen717

还不如直接看英文

8055

高手给总结成一句话呗，看得不知所云。那意思是陶瓷封装的LM399其实就很不错了

youngliu

8055 发表于 2015-1-5 09:36
高手给总结成一句话呗，看得不知所云。那意思是陶瓷封装的LM399其实就很不错了

LM399是金封的，只不过外面套了一个聚砜保温罩

8055

youngliu 发表于 2015-1-5 10:11
LM399是金封的，只不过外面套了一个聚砜保温罩

明白了，LM399只有外面树脂壳的，对吧。

mercyau

8055 发表于 2015-1-5 10:21
明白了，LM399只有外面树脂壳的，对吧。

人家说6个399并联会更好，设计得当的话。

另外建议使用新LTZ1000的把LTZ扔到125度老化2周，

各位，准备好扔了没

hu_lin

译文看得我想骂小学语文老师了

pryprypry

删去了一些与38hot无关的或者坛友们不关心的东西,只保留了有用信息.翻译如下,请大家斧正.

筒子们大家好,
我刚和Bob通完电话,他时间比较紧,所以我没法问完我们的全部问题.我得到答案的问题有以下几个:
1>[供大家参考]LTZ1000数据表里面的那个电路及LTZ的其他应用笔记都是Bob写的,不是Williams.
2>LTZ1000的稳压调整与其说是控制电压还不如说是控制功率.如果你很好的控制功率的话,那么电压稳定性自然而然也就达到了.
3>LTZ1000A和LTZ1000的晶片与封装的连接方式不同,但是他们都和外部的管脚应力很好的隔离开来.管脚机械应力对两个器件都有影响,但是A版本所受的影响要小得多.这种影响主要表现为随大气压变化而引起的输出电压漂移.
4>已经过去了20年,所以他不记得具体的数字了,但是Q1的额定集电极电流只有几百微安.Q2的额定集电极电流有一个毫安左右,齐纳的额定电流还能再多点.
5>他们(本)可以为这个器件制作一个LTspice模型,但是温度变化的影响极难模拟,而且这个产品的市场太小,不足以支撑这个模型的研发.他说最好的办法是把这个电路做出来然后实验决定它的性能.
6>我告诉他我想要一个电压传递基准,他说更好的方法是用至少6个LM399并连起来.他说加速老化的方法就是把这些LM399放在一个125度的烘箱里面工作2周,这相当于1000小时的正常工作时间.(在这个过程中)任何漂移较大的LM399都可以筛掉. LM399比LTZ对PCB机械应力要敏感的多,所以LM399在安装时应该离开PCB的表面一些距离. LM399的长期稳定性直接取决于用在加热器上的能量多少--这可以使用热绝缘得到最小化--热绝缘越好,那么耗费在加热上的能量就越少,长稳就越好. LM399被关闭时不老化,而且也没有回滞,所以在不用这个基准的时候应该把它关掉,在你使用或者校准的时候再提前几个钟头开启.这是保证长期漂移最小化的办法.
7>需要注意的是,对于LM399的设计,在PCB上面开槽和加热绝缘材料是有用的.加热器的功率越小,那么输出电压就越稳定.所以,在这种状况下,开槽和热绝缘是对电压稳定性是有帮助的.哦,他还提到LM399的齐纳电流在1mA是稳定性最好的. 齐纳电流的稳定性越好,输出电压的稳定性越高.他说齐纳电流每变化1uA,输出电压就变化1uV.
8>对于所有的基准而言,他们在高温的老化速度确实较快.所以,因为LTZ1000能比LTZ1000A的工作温度低10度,所以长期漂移在其他外部条件相同的状况下会小一半.但是,A版本有其他的优点,比如大气压对它的影响较小等.
9>对于LM399和LTZ,他说一个较好的加速老化措施是使他们在一个125度的烘箱中工作2周.然后,你可以在正常工作温度下反复开关10-15次电源,这样的话应该会让他们稳定下来.这个过程应该能除去绝大部分的初始漂移.
10>如果很好地绝缘的话,LM339的温飘在0.1ppm/度到0.2ppm/度之间--数据表是非常保守的.注意那些数字表的制造商并没有增加额外的热绝缘措施,当然在上下加上这些材料会更好.
11>他们在准备发布更多的LS8(8脚陶瓷封装)的器件,他们应该今年年底能出来.有一些器件LS8装不下,所以他们会用一个更大的LCC封装,他说1021系列在准备发布的LS8封装的器件之列.
12>LCC封装的引出仍然使用了可伐合金,因此热电势的问题仍然存在.这些器件在安装到板上之后应该隔绝空气流动(就像TO封装的一样).
13>LTZ并不需要像LM399一样在安装时离开PCB板一定距离,因为在这个封装内部有独一无二的抗应力设计.
14>他们不会为LTZ做一个参考设计--这是一个不值得花时间去开发的小众产品.
15>TO封装的内部是干空气(甚至不是氮气).因此可能会导致一些性能退化,但是目前为止还没有任何器件因此退化.
16>LTZ1000比LTZ1000A的功率大得多,所以对于电池供电的设计来说,最好是用LTZ1000A,并且对它进行热绝缘以节省能源.
17>想要在LTZ上得到0温度系数是很可能无法实现的.你需要让Q1工作在1uA,这是不现实的.
18>他说不必要用LTC2057,因为齐纳管的噪声和漂移贡献比LT1013大得多.Bob说你几乎可以用任何运放,而且漂移不会因为使用了精度差的运放而受很大影响.(但是我仍然要用LTC2057,因为他们像爆米花一样便宜,而且噪声很低.在后级电路中我的确需要一个零飘的放大器,因此保持BOM上的元件数量尽量少是更经济的).
19>LTFLU-1和LTZ1000内部的齐纳管是完全相同的.他说即便和Fluke的销售合同之中的排他性部分已经失效了,他们也不会公开销售这个器件,因为他们不想惹毛那个从他们这里每年购买数百万美元的其他器件的客户(暗指Fluke).即便他们真的要卖这个LTFLU-1,这个器件也没有表征数据,而且也没有数据表--仅仅做这些东西就要花很多时间. 总而言之是不会卖的.

祝好,
Ken

fffofo

pryprypry 发表于 2015-1-7 00:03
删去了一些与38hot无关的或者坛友们不关心的东西,只保留了有用信息.翻译如下,请大家斧正.

筒子们大家好, ...

这次我必须顶你，赞一个！

zsxlh

超赞！

jj3055

都怪我没常来，没注意16楼，白白浪费一个晚上去翻译

3458A

这个必须得学习

youngliu

pryprypry 发表于 2015-1-7 00:03
删去了一些与38hot无关的或者坛友们不关心的东西,只保留了有用信息.翻译如下,请大家斧正.

筒子们大家好, ...

翻译得很好

04102

非常有意思，学习了：）

aihao

pryprypry 干的不错！这下看起来爽多了。