Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x - Page 1
Forum section: electronics / general

author: zlymex
author_rank: Frequent Contributor
timestamp: September 28, 2016, 11:39:32 am
content: Brief facts- 2DW23x series is a Chinese brand temperature compensated Zener reference- There are two identical zener diodes connected in back to back manner in a 3-lead TO-39 package.- Norminal voltage 6.0V t0 6.5V- Norminal zero-TC current ranges from 5mA to 15mA depending on types.- Datasheet(in Chinese)http://www.chinaeds.com/zl/%E5%B8%B8%E7%94%A8IC%5C2%5C2D%5C2DW230.pdfWhy 2DW23xThese 2DW23x series(2DW232, 2DW233, 2DW234, 2DW235) has been around for many year and was probably the only 'reference grade' zener in China. Previously known as 2DW7C and changed name about ten years ago. There were/are many manufacturers making these devices and I have tons of them. The performance varies according to makers very much and generally are poor (aging rate, tempco, noise). I've never use them in my designs/circuits.However, people discovered that there is this Shanghai 17th Radio Factory making this particular Diamond brand(there is a diamond symbol on face of each device) with exceptional low noise, even lower than that of LTZ1000. I didn't believed, but there are a lot of buying/teardown/discuss about it:http://bbs.38hot.net/forum.php?mod=viewthread&tid=49306http://bbs.38hot.net/forum.php?mod=viewthread&tid=84620http://bbs.38hot.net/forum.php?mod=viewthread&tid=119921http://bbs.38hot.net/forum.php?mod=viewthread&tid=120264http://bbs.38hot.net/forum.php?mod=viewthread&tid=120731So, I built my own noise meter recently and bought some samples. At first, the noise tested is not good, 1.2uVp-p, same or slightly inferior to LTZ1000. However, some one soon pointed out that the power supply might be the problem. After I changed the power source to batteries, I got even better result than others: 0.4uVp-p at 5mA, which is one third of LTZ1000. I swapped devices, altered current, measured my other LTZ1000 based voltages(4910, 732A, 732B etc) as reference, and I bought more 2DW23x from other e-stores, they all show this ultra-low noise characteristic.AvailabilityI bought about 200 unit of 2DW233 from here:https://item.taobao.com/item.htm?spm=a1z09.2.0.0.gpf2Zk&id=35815633601Then I bought 550 unit of 2DW234 from another seller.There are many sellers at Aliexpress selling these cheaply but only buy those with diamond mark on the top such ashttp://www.aliexpress.com/item/Free-shipping-2DW233-DIP3/32433963421.htmlhttp://www.aliexpress.com/item/hot-spot-10pcs-2DW232-new-original-in-stock/32637084815.htmlhttps://www.aliexpress.com/item/High-quality-10Pcs-2DW234-2DW235-2DW236-New/32527935820.htmlBe warned, I got these links by searching only. Someone was buying one of the entries and did not receive the package in 75 days.My plan to test/use1. A very simple circuit(batteries+resistor) to test/verify noise, done.2. A simple circuit to test/seek the zero-TC point, partially done.For a given device at given zener current, there is a convex shape of voltage-temperature curve and there is a peak voltage which is the zero-TC point for temperature.Because of this, for a given device at given temp, there is a convex shape of voltage-current curve and there is a peak voltage which is the zero-TC point for zener current.The type number(2DW232, 2DW233) indicating different nominal zener current for this zero-TC point. For instance, the zero-TC current of 2DW232 is 5mA, the zero-TC current of 2DW233 is 7.5mA, the zero-TC current of 2DW234 is 10mA, and so on.But in reality, there is not much difference. A device of any type may show zero-TC current at any value ranging from 4mA to 20mA, therefore, there is need to test every device for it's zero-TC current.3. Accelerate agingBoil at 100 degree C and freeze at -15 degree C, repeat the cycle many times.4. A circuit to test aging rate etc.- build many to test simultaneously- characterize TC- test by continuous power up, power down/up, mild thermal shock, mechanical shockThe zener current(5mA to 10mA) is supplied by an foil resistor R1 from the final 10V. The current should be stable to 25ppm annually.R2 and R3 are foil divider pair, the exact value is no very important but this 10V should be stable to 15ppm annually(assuming 2DW233 is stable).I'll use AD707AH because I have a lot of them and the noise is not too bad(0.23uVpp, 14pAp-p).5. OthersI've built one prototype but the noise is not as low as expected probably because there is no heat sink/thermal lag.ReferenceThere is a Chinese military standard SJ 50033/150-2002 on 2DW230-2DW236.http://doc.mbalib.com/view/7ff38949056ec076fcf871d4e67ec0f4.htmlMore datasheet from the industryhttp://doc.mbalib.com/view/1a1945b2dcc8911e2a82b0f5ff52fc0f.htmlI also found an old article(dated 1986, attached but in Chinese), the author were obviously from Shanghai 17th radio factory describing this 'superb' zener of Diamond brand.He said, from 1982, the factory began a profound revolutionary change of the process structure of the 2DW230-2DW236 series making it rival similar products abroad in term of low noise and low drift. There are some test results in the article but the author did not tell anything about their new process. There was someone who tested an 2DW234 dated 1987 and got 3.2uVp-p noise, compatible with what have described in the article(http://bbs.38hot.net/forum.php?mod=viewthread&tid=120264). He also tested another 2DW234 dated 2013 and got 0.57uVp-p noise. This means that there must be another change of the process structure in Shanghai 17th radio factory between 1987 to 2013. One thing for certain is that they changed the internal connection of two zener from common anode(as can be seen from above two internal diagrams) to common cathode.I took apart one(of 2DW234), here is the photo by my card camera plus a magnifierSomeone at 38hot(archwang) took a much better inside photo of 2DW234 dated 2013(see attached)

author: zlymex
author_rank: Frequent Contributor
timestamp: September 28, 2016, 11:42:44 am
content: Low frequency noise testBy my DIY noise meter(https://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/), I tested some 2DW233.For a given zener, the LF noise is inverse proportional to the square root of applied current. I plotted the curve for some well known zeners with 2DW23x which shows 2DW232 is about 2.54 times better noise wise or 6.5 times better current wise.T.C. testAging test

author: Kleinstein
author_rank: Super Contributor
timestamp: September 28, 2016, 03:29:06 pm
content: With the two references in one case one could use the second zener as a normal diode to sene the chip temperature.Form the internal pictures shown in one of the links, it looks like the chip itself is covered in a drop if transparent glue (e.g. epoxy). So heating to more than 100-120 C (and the speed of cooling from there) might have an influence on the glue and thus performance / aging.With the relatively high power, there can be temperature fluctuation due to turbulent air flow - this might look very much like 1/f noise. Often one covers sensitve circuits with a kind of foam / fiber.

author: zlymex
author_rank: Frequent Contributor
timestamp: September 28, 2016, 03:52:27 pm
content: Quote from: Kleinstein on September 28, 2016, 03:29:06 pmI think you are absolutely correct on these points. I'm going to design an temperature oven by using the forward biased diode. I also boiled 200 pieces for high temperature cycle but not higher.

author: Cerebus
author_rank: Super Contributor
timestamp: September 28, 2016, 09:14:20 pm
content: All very interesting, thanks for posting this.

author: quarks
author_rank: Frequent Contributor
timestamp: September 29, 2016, 08:00:21 am
content: Bookmark!Thanks a lot for sharing.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: September 29, 2016, 09:18:23 am
content: +1

author: retrolefty
author_rank: Super Contributor
timestamp: September 29, 2016, 11:54:38 am
content: Quote from: quarks on September 29, 2016, 08:00:21 amDitto

author: WN1X
author_rank: Unknown
timestamp: September 29, 2016, 02:42:37 pm
content: Quote from: zlymex on September 28, 2016, 03:52:27 pmZener diode soup...my favoriteVery interesting thread...I look forward to future updates

author: Theboel
author_rank: Frequent Contributor
timestamp: October 06, 2016, 04:20:56 am
content: Try to contact some seller who offer this Zener but no luck, perhaps some else luckier than me can share information

author: zlymex
author_rank: Frequent Contributor
timestamp: October 06, 2016, 04:04:22 pm
content: Quote from: Theboel on October 06, 2016, 04:20:56 am1st Oct. to 7th Oct. is a Holiday in China.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: October 07, 2016, 08:57:58 am
content: I'll let this next few days pass, because of the back orders that the sellers might have, and next week I'll try to buy some 10 to 30 units and try to make 2 or 3 boards and test over time for drift.

author: Theboel
author_rank: Frequent Contributor
timestamp: October 07, 2016, 01:10:00 pm
content: @ Zlymex,Thank You for the information. but still if anybody outside china can buy it online I like to know the information.btw, I like to use this zener for discrete ADC/DAC in audio freq range application anyone has experience about that ?

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: October 13, 2016, 04:57:13 pm
content: Zlymex how do you compare 2DW232 with LTZ1000A when you are measuring them with the gears that use LTZ1000A as their reference and claiming that they are better than LTZ1000A also I have another question, how they characterized the LTZ1000A against what beast?

author: Squantor
author_rank: Contributor
timestamp: October 14, 2016, 07:08:11 am
content: Quote from: Theboel on October 07, 2016, 01:10:00 pmI ordered at this store:https://www.aliexpress.com/item/2DW230-2DW231-2DW232-2DW233-2DW234/966304921.htmlIt is still underway to me, hopefully they are the "diamond" brand zeners, a lot of people are using the same pictures. I will report back as soon as I get them. One thing to notice with this vendor is that you need to send him a message with what type you want to buy.

author: VintageNut
author_rank: Frequent Contributor
timestamp: October 21, 2016, 05:25:26 pm
content: I ordered 30 pcs from the below link. Only 10 pcs arrivedhttps://www.aliexpress.com/item/High-quality-10Pcs-2DW234-2DW235-2DW236-New/32527935820.html?spm=2114.13010608.0.0.lA0McyThe parts arrived but they do not have the diamond mark on top. There is no mark on top. The part number is written in blue on the side with no visible production date. The logo in blue is mostly a blur and not readable.I have contacted the seller and asked for a refund. I paid $20 for 30 pcs to be sent to me. My guess is that most of these sellers are selling garbage parts with a picture of the good stuff on their page.

author: JS
author_rank: Frequent Contributor
timestamp: October 21, 2016, 07:03:35 pm
content: Quote from: VintageNut on October 21, 2016, 05:25:26 pmEven if they are doing that makes no sense to not send the specified quantity...JS

author: VintageNut
author_rank: Frequent Contributor
timestamp: October 21, 2016, 09:16:43 pm
content: Quote from: JS on October 21, 2016, 07:03:35 pmI stand corrected. The other 20 pcs were balled up in what looked like filler packing. So they did send all 30 but these are not what is pictured. Many of the sellers of these have the same picture posted.I picked a different seller and sent an email asking if the parts are exactly as pictured. We shall see what happens. No big deal one way or the other. It would be good to get 20 to 30 of these and let a batch cook for a while.

author: zlymex
author_rank: Frequent Contributor
timestamp: October 22, 2016, 02:08:13 am
content: That's very unfortunate @VintageNut. Anyway, only the diamond brand has low noise property, others are just garbage.

author: martinr33
author_rank: Frequent Contributor
timestamp: October 22, 2016, 06:31:18 am
content: I have managed to get some via TaoBao. They look genuine. I'll see if I can persuade my wife to put them up for sale on her web site.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 22, 2016, 07:39:46 am
content: Are there data on how good those references are in respect to drift. The kind of glue on top of the chip is not that promising, as it might age, especially at higher temperature.

author: janode
author_rank: Newbie
timestamp: October 22, 2016, 10:13:29 am
content: I tried my luck with "AIX ELECTROINC CO.,LTD":https://www.aliexpress.com/item/2DW233-DIP3/32354191799.htmlOh well, not so surprisingly the components don't look the same as in the picture. There's poor quality blue printing on the side, not the top, of the components. Leads are gold colour.. actually very close to colour of my 21K gold ring. Weird if they bothered to waste actual gold on those. I would love to add here the head banging smiley, because it's so great, but I'm not really disappointed.

author: VintageNut
author_rank: Frequent Contributor
timestamp: October 22, 2016, 11:28:30 am
content: Quote from: martinr33 on October 22, 2016, 06:31:18 amThat would be cool and very helpful.How did you purchase via Taobao? I could not get the website to be usable in english.

author: SeanB
author_rank: Super Contributor
timestamp: October 22, 2016, 11:57:10 am
content: Quote from: janode on October 22, 2016, 10:13:29 amMy bet is they simplt relabelled old stock transistors and sold them. Try them for gain, it might be a Germanium PNP transistor with a badge job.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: October 22, 2016, 12:03:46 pm
content: For those interested in the 2DW2xx, maybe zlymex can help out, since he has access to tabao and know's what could be real, we could buy them for the ones that want them, and send them out, if he want to get this kind of trouble. :-)