Author Topic: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x  (Read 128532 times)

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Offline bertik

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #125 on: November 06, 2016, 08:12:42 pm »
What about using the second zener to reduce noise instead?  Feeding it to a separate opamp and then combining reduces the noise by a factor of 1/sqrt(2). While not much this would give an easy improvement for the price of an extra opamp.

Using it just for temp sensing seems a sacrilege.. that could be easily done by gluing a thermistor on top of it.

-BK
 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #126 on: November 06, 2016, 09:22:04 pm »
Even with just one diode used, the noise is already really low - e.g. better than an OP07, OP177 or AD707 which are typical candidates for scaling the voltage. The current to get a low TC is already quite high (e.g 5 mA range) - more current is more of a problem it you don't want the chip to heat up too much.

Having a temperature sensor directly on the chip can really help to stabilize or just measure the temperature.  So I would consider this the more practical use for the second diode.
 
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Offline Tazz

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #127 on: November 06, 2016, 09:31:06 pm »
Kleinstein, I second you for the use of the second diode
 

Online Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #128 on: November 06, 2016, 10:47:02 pm »
Zlymex:

Isnt the 2nd diode already used forward biased as temperature compensation diode?
I cannot get this clear from your description.
In this case you do not need to think about further noise reduction.

Or are there 2 temperature compensated diodes (2 zeners + 2 diodes) in one package?
In this case you cannot read the temperature. (because the zener voltage is in series to the compensation diode).

with best regards

Andreas
 

Offline plesa

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #129 on: November 06, 2016, 11:33:37 pm »
Zlymex:

Isnt the 2nd diode already used forward biased as temperature compensation diode?
I cannot get this clear from your description.
In this case you do not need to think about further noise reduction.

Or are there 2 temperature compensated diodes (2 zeners + 2 diodes) in one package?
In this case you cannot read the temperature. (because the zener voltage is in series to the compensation diode).

with best regards

Andreas

There are only two zeners, back to back and common anode connected to package.
So there is first order temperature compensation - zener avalanche  diode.
On first piece I will have I'm going to remove epoxy and check it under microscope.
http://www.eevblog.com/forum/metrology/ultra-low-noise-reference-2dw232-2dw233-2dw23x/
It is the same like used in zeners like 1N82x.
« Last Edit: November 06, 2016, 11:35:58 pm by plesa »
 

Online Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #130 on: November 06, 2016, 11:52:16 pm »
The 1N82x has a normal diode in series to the zener.

with best regards

Andreas
 

Offline plesa

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #131 on: November 06, 2016, 11:59:06 pm »
The 1N82x has a normal diode in series to the zener.

with best regards

Andreas

OK, and do you thin that doping level will make noticeable difference in tempco of forward biased diode?
 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #132 on: November 07, 2016, 12:18:28 am »
I suggest a flexible arrangement to use the second diode --
(a) To be able to use it forward biased to measure temperature. 
(b) Perhaps it could even be used in forward or reverse to help control temperature as well (small addition to local temperature as controlled)?
(c) In reverse as a voltage reference.

When used in reverse as a second voltage reference one could
(d) Get a negative reference voltage to match the positive which could be useful for miscellaneous purposes.
(e) Ger a negative reference voltage to match the positive one and so the back to back series voltage could be measured like a null measurement to look for differential drift of the two diodes.  This could be useful for stability tracking of the voltage outputs.
(f) The pair of voltages could be assessed independently for noise and drift so one could get two measurements from one unit. 
(g) It could be determined how good the matching of characteristics are between the two diodes which may or may not be monolithic adjacent pads on the same wafer or which could be two different die which are likely from the same wafer and may or may not generally be from adjacent sites. In any case knowing the matching of the two devices that ought to be as similar as possible could indicate the stability of performance of either / both over time and use.
(h) If one device is noisy the other one could be used as a primary reference output.   
(i) and of course be bringing out the signal forward / reverse tempco measurement can be made for use in analysis & R&D of subsequent uses / circuits whether for purposes of reference or temperature controller.

If for practical circuit uses there is to be any use cases of using the dual diodes to make bipolar references then it should be characterized as such with a constant current flowing through both diodes to see how that use case could perform.
 
What about using the second zener to reduce noise instead?  Feeding it to a separate opamp and then combining reduces the noise by a factor of 1/sqrt(2). While not much this would give an easy improvement for the price of an extra opamp.

Using it just for temp sensing seems a sacrilege.. that could be easily done by gluing a thermistor on top of it.

-BK
 

Offline Gyro

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #133 on: November 07, 2016, 12:25:40 am »
Has anyone managed to find a more comprehensive datasheet for these parts? I successfully downloaded the one that zlymex linked in his first post (the 2 page Shen Xin one) but didn't have any success downloading the ones he linked later.

I've attached one pdf datasheet that I found (SJ brand), it appears to include lots of environmental test requirents but is mostly incomprehensible to me. I guess one from the 17th Radio Factory itself would be the holy grail. It, or a translation, might help answer some of the questions that are coming up.

Chris

(Edit: typo)
« Last Edit: November 07, 2016, 12:46:50 am by Gyro »
Chris

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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #134 on: November 07, 2016, 12:49:57 am »
It is a good question whether the two zeners are just normal zener diodes (like 6.2 V reference diodes) or they are supposed to used as a pair in series as a 7 V reference more like the 1N829 or similar.

There are both ways to get a low TC reference diode at the right current: either just a suitable zener diode at about 5-6 V or a compensated version with a zener and normal diode in series like in the 1N829, usually in the 7 V range or higher.

As the voltage is only 6.2 V, I would expect a relatively normal zener. We don't really know much about the internal details - at least they seem to be much lower noise than normal zener diodes. So there is like a more or less secret detail that makes these diodes so special.

Normally the TC of a silicon diode in forward direction is not depending on details of the diode: usually one has a linear temperature dependence that extrapolates to 1.2 V at 0 K. Higher current gives a higher voltage and thus lower TC. Thus a diode with 600 mV forward drop at 300 K will have a -2 mV/K slope.

As the diodes are connected common anode, there is no way to use them in series as a 12.4 V ref. One might be able to use the second diode as a backup to check for drift - but this would likely be better with a completely separate one.

With no detailed DS one might want to do a few measurements, e.g. voltage as a function of current an temperature to get TC and differential resistance. To really get the best working conditions one might need these data for the individual units anyway.
 

Online Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #135 on: November 07, 2016, 01:26:34 am »
It is a good question whether the two zeners are just normal zener diodes (like 6.2 V reference diodes) or they are supposed to used as a pair in series as a 7 V reference more like the 1N829 or similar.

There are both ways to get a low TC reference diode at the right current: either just a suitable zener diode at about 5-6 V or a compensated version with a zener and normal diode in series like in the 1N829, usually in the 7 V range or higher.

As the voltage is only 6.2 V, I would expect a relatively normal zener. We don't really know much about the internal details - at least they seem to be much lower noise than normal zener diodes. So there is like a more or less secret detail that makes these diodes so special.

Hello,

I think you have never had a 1N829 in hand.
The 1N829 has around 6.4V. (one of the usual voltages of temperature compensated zeners).
It is a normal diode 0.7V (-2mV/K) and a Zener (around 5.7 so +2mV/K) in series.
If you measure the 1N829 zener in "forward direction" you will find the breakdown voltage of the normal diode.
(which is beyond 15 V).

with best regards

Andreas
 

Offline Gyro

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #136 on: November 07, 2016, 02:47:26 am »
I happened to measure a few 1N827 to 829 a few days ago, they were in the 6.2-6.3V range. The highest was a very old ex Solartron 1N829A which came out at 6.37V iirc, all at 7.5mA. It's only LM399, LTZ etc that are in the 6.95V range.

If that is in the same range as the 2DW233 then it is either a zener+series diode or a higher voltage zener with unsusual TC characteristics.  If it is a zener + diode combo then that will exclude using the second one as a sense diode... 1N82x don't conduct backwards (forwards in the conventional sense), the series diode is reverse biased.  :-\

This is the sort of thing a more comprehensive (and comprehensible?) datasheet would tell us.
« Last Edit: November 07, 2016, 02:57:40 am by Gyro »
Chris

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Online Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #137 on: November 07, 2016, 03:01:42 am »
Hello,

in the 1N82x series there are also some back to back zeners available (1N824) (but without center tap)
in this case both directions will have the 5.9-6.5 V zener voltage.
http://www.microsemi.com/document-portal/doc_download/10940-sa6-3-pdf

The trick of having a forward biased diode and a zener diode is that there will be a "zero TC" current
where the diode and zener TC are compensated to near zero over a small temperature range.

with best regards

Andreas


 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #138 on: November 07, 2016, 04:19:06 am »
Someone claimed that the 1N823 also has superior noise characteristics, though I don't have any to test and there are not specific details.
http://www.diyaudio.com/forums/parts/35821-some-noise-measurements-leds-zener-diodes-12.html#post960894
"By chance I found that the noise of an 1N823 (6.2V temperature compensated) is dramatically less than that of ordinary zeners, even when you need more than one for getting the required voltage."

If I recall correctly I think I saw that the noise of a zener is related to its area and current density which makes sense if a larger area is like putting more devices in parallel.  If that is the case then perhaps part of the lower noise of such devices could simply be that they are larger area devices?

Hello,

in the 1N82x series there are also some back to back zeners available (1N824) (but without center tap)
in this case both directions will have the 5.9-6.5 V zener voltage.
http://www.microsemi.com/document-portal/doc_download/10940-sa6-3-pdf

The trick of having a forward biased diode and a zener diode is that there will be a "zero TC" current
where the diode and zener TC are compensated to near zero over a small temperature range.

with best regards

Andreas
 

Online Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #139 on: November 07, 2016, 05:22:53 am »
Hello,

my measurements on several 1N829A (which are only specified for lesser T.C. (at 7.5mA) than 1N823) range from 2uVpp to 22uVpp 1/f noise (0.1 .. 10Hz).
This depends much on manufacturer.
I do not know if the quality nowadays is still the same...

The lesser noise (compared to higher voltage zeners in the link) might result from lower dynamic resistance.
Which is below 10 Ohms for around 6V compared to around 100 Ohms or more for higher voltage zeners.

With best regards

Andreas

 
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Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #140 on: November 07, 2016, 04:10:05 pm »
Hello, thank you very much, that is interesting and good information about your findings with these parts.

Hello,

my measurements on several 1N829A (which are only specified for lesser T.C. (at 7.5mA) than 1N823) range from 2uVpp to 22uVpp 1/f noise (0.1 .. 10Hz).
This depends much on manufacturer.
I do not know if the quality nowadays is still the same...

The lesser noise (compared to higher voltage zeners in the link) might result from lower dynamic resistance.
Which is below 10 Ohms for around 6V compared to around 100 Ohms or more for higher voltage zeners.

With best regards

Andreas
 

Online technix

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #141 on: November 07, 2016, 04:31:12 pm »
I have talked with factory that originally made those 2DW233's, Shanghai No. 17 Radio Factory, and I can order them for you fresh from the factory if you want to.
 
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #142 on: November 07, 2016, 04:44:35 pm »

If I recall correctly I think I saw that the noise of a zener is related to its area and current density which makes sense if a larger area is like putting more devices in parallel.  If that is the case then perhaps part of the lower noise of such devices could simply be that they are larger area devices?

That is not the case. If we parallel four identical devices and run the same current, the noise would be the same.
Parallel four devices and the noise is halved, this only happens if the total current is quadrupled. but this is equivalent to running the larger current on a single device.
The advantage of large area is the ability to run at larger current.
"2DW232 has much better noise than LTZ1000", this is compared at the same zener current.
 
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Offline 2N3055

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #143 on: November 07, 2016, 06:36:16 pm »
You can consider that large crystal is equivalent of many small crystals connected in parallel. All stochastic noise related events combine same as they would from dozens of separate parallel connected diodes..
Of course,  if  you run it as same current density as with separate diodes...
 
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Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #144 on: November 08, 2016, 12:57:49 pm »
Thank you very much, technix!

What information did you receive about prices for various quantity ranges?

I would be interested to order some, maybe others here will also be so.

I have talked with factory that originally made those 2DW233's, Shanghai No. 17 Radio Factory, and I can order them for you fresh from the factory if you want to.
 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #145 on: November 08, 2016, 01:01:21 pm »
Thank you very much, zlymex, and 2N3055, your explanations are logical.
 

That is not the case. If we parallel four identical devices and run the same current, the noise would be the same.
Parallel four devices and the noise is halved, this only happens if the total current is quadrupled. but this is equivalent to running the larger current on a single device.
The advantage of large area is the ability to run at larger current.
"2DW232 has much better noise than LTZ1000", this is compared at the same zener current.

You can consider that large crystal is equivalent of many small crystals connected in parallel. All stochastic noise related events combine same as they would from dozens of separate parallel connected diodes..
Of course,  if  you run it as same current density as with separate diodes...
 

Online technix

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #146 on: November 08, 2016, 03:07:46 pm »
Thank you very much, technix!

What information did you receive about prices for various quantity ranges?

I would be interested to order some, maybe others here will also be so.

I have talked with factory that originally made those 2DW233's, Shanghai No. 17 Radio Factory, and I can order them for you fresh from the factory if you want to.

They gave me a solid 75 US cents each regardless of amount, and for order more than 50 (a whole pack) they will pay for the shipping from their factory to my home. When I send it on the shipping cost would be $5 for less than 2kg.
 

Online technix

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #147 on: November 08, 2016, 03:33:26 pm »
Here is the test circuit I am going to use when selecting the 2DW233 for you.

ADC is the built-in 10-bit unit inside ATmega328P, while DAC is TLC5615 (8-bit) referenced from ADR03B. The microcontroller will perform a search to find the best approximate of the zero TC point in the range of 0mA to about 50mA.
« Last Edit: November 08, 2016, 04:59:11 pm by technix »
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #148 on: November 08, 2016, 10:33:32 pm »
Here is the test circuit I am going to use when selecting the 2DW233 for you.

ADC is the built-in 10-bit unit inside ATmega328P, while DAC is TLC5615 (8-bit) referenced from ADR03B. The microcontroller will perform a search to find the best approximate of the zero TC point in the range of 0mA to about 50mA.
2DW232 is very sensitive to the supply current, therefore I suspect the short term stabllity of the current mirror unless they are paired and thermally bonded.

Theoritically, to test the zero T.C. points(there are many for one device), there is the need both for varying the current and the temperature.
Practically, a step current can be used, then monitor the voltage variation direction to determin whether the current is Ok.
 

Online technix

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #149 on: November 08, 2016, 11:40:45 pm »
Here is the test circuit I am going to use when selecting the 2DW233 for you.

ADC is the built-in 10-bit unit inside ATmega328P, while DAC is TLC5615 (8-bit) referenced from ADR03B. The microcontroller will perform a search to find the best approximate of the zero TC point in the range of 0mA to about 50mA.
2DW232 is very sensitive to the supply current, therefore I suspect the short term stabllity of the current mirror unless they are paired and thermally bonded.

Theoritically, to test the zero T.C. points(there are many for one device), there is the need both for varying the current and the temperature.
Practically, a step current can be used, then monitor the voltage variation direction to determin whether the current is Ok.

In practise I am using the BCV62 for the current mirror - the two PNPs are built on the same piece of silicon and are factory matched. I have already breadboarded the setup and tests on my stock of 1N4728 and 1N4734 are showing the correct behavior. I can scan through 0 to 25mA (I ended up using a 199.7 ohm resistor instead of 100 ohm one as the current sense resistor) at about 0.1mA step and measure the voltage with this automated jig.

I will implement a faster search algorithm that can find the optimal current on the MCU and a component insert sense feature, so when the parts arrive I can bulk test them very rapidly.
 


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